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parts, whilst the current edition is in four parts. The added part is somewhat of a jumble, inasmuch as it is supplementary of each of the first three parts. The scheme of the book is not apparent from the list of contents, and this omission results in confusion. Whilst, however, the arrangement of the book is bad, the matter is good. In skilful hands, indeed, the material which is here accumulated might have been very attractively presented. At p. 132, a dozen pages are commenced on the pests of the farm, whilst another dozen pages devoted to the same subject begin on p. 180. At p. 71, the reader enters upon 30 pages about manures, and at p. 167 he gets a further dozen pages also upon manures, f And so on.

With reference to the fixation of nitrogen by leguminous plants, mention is made of the presence on the roots of these plants of " little bag-like enlargements, or tubercles as they are called." It is unfortunate that this effort should be made to associate the pathological term '■'tubercle" with these structures. The word "nodule " is much preferable, and is not less explanatory.

Despite the fact that the book has been written to enable candidates to "pass an examination," it is as i useful and trustworthy a little treatise of the kind as [ we have seen.

Elementary Trigonometry. By J. M. Dyer and Rev.

R. H. Whitcombe. (London : George Bell, 1891.) The title of this book is on all fours with the contents. The work is well adapted for school use. The explanations of book-work are clearly expressed, and the text is amply illustrated by a store of exercises. Sufficient ground is covered to meet the wants of average Army pupils.

We have detected errata in the text on pp. 21, 30, 36,59,61,62,65, 67,74, 80, 101, 136, 153. The major part of the proof-sheets has been carefully gone over, but occasionally, as we have indicated, the authors have nodded. The printing in places, in our copy, is defective. But these faults only slightly mar a work which treats a hackneyed subject with all the freshness one can look for in an elementary text-book.


[ The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of Natv RE. No notice is taken of anonymous communications. ]

Opportunity for a Naturalist.

Since the completion of " Argentine Ornithology," in which was given an account of the 434 species of birds then known to occur in the Argentine Republic, Mr. Arthur Holland, of the Estancia Espartilla, and Mr. J. Graham Kerr, of the Pilcomayo Expedition, have made excellent contributions to the same subject, and have added some 30 species to the Argentine avifauna. But much more remains to be done, and, in continuation of the work, I am now anxious to get a good series of birds from Uruguay, the fauna of which, so far as we know it, does not appear to differ materially from that of its neighbouring Republic. For this purpose I have made arrangements with a friend to take in a naturalist at his Estancia, near Minas, about sixty miles from Monte Video, and am looking for a qualified collector to occupy the post. His necessary expenses will be met, hut his further remuneration must de end, more or less, on the results obtained. May I ask the aid of Nature to make known this eligible opportunity for a young naturalist who can make good birds'-skins, and is anxious to pass a few months in a foreign clime? V. L. Sci.ATEK.

3 Hanover Square, London, W.

Warning Colours. Mr. Beddakd, in his letter published in Nature of November 26 (p. 78), calls attention to Dr. Eisig's suggestion that

those bright colours of animals which have hitherto been regarded as of warning significance are merely the subs.ances which confer the taste, and that therefore the older interpretation is unnecessary and in fact erroneous. The writer furthermore implies that Dr. Eisig's views are not alluded to by those who have written upon animal colours, because they have escaped their attention. There is, however, another possible explanation of such neglect, and one which in my own case is certainly the correct one—viz. that the views in question appear to be so inherently improbable that a large body of confirmatory evidence is required before they demand attention. I do not by ibis mean to suggest that the unpalatable attribute may not possess a bright colour: this is certainly often the case, especially with the secretions expelled by many insects when they are irritated. But it is highly improbable that these facts afford any refutation of the theory of " warning colours"—that is, of the view which regards the bright and conspicuous colouring as nn indication (in mimetic forms a false indication) of some unpleasant attribute, whelher associated or unassociated with the colour itself. And as regards the bright colours of Lepidopterous imagines, such association is, tosay the least of it, entirely unproved. It by no means follows that the yellow colouring of the brimstone and other butterflies is disagreeable in flavour because it "is due to a substance formed as a urinary pigment." And the relation of many animal colours to these pigments by no means necessarily implies unpalatability. Again, it would be impossible to regard merely as a coincidence the fact that the substances in question almost invariably produce a conspicuous appearance, and, furthermore, produce it in a variety of ways. Such an appearance is, as is well known, not merely due to the individual colours, but to their mutual arrangement and relationship. It is due, moreover, to a variety of physical principles, for the production of white is very different from the production of the colours which are so often contrasted with it. Conspicuous effects are furthermore often gained without the use of pigment, as ift the brilliantly metallic pupae of Euplaa core and of Mechanitis lysimnia. Hence the contention thatMhe bright colour of distasteful insects is a mere incident of chemical composition which has been selected on other accounts is so inherently improbable that it would require a large body of evidence to support it.

But perhaps the strongest argument against the view is that it creates such an artificial distinction between inedibility due to mere unpalatability, and that due to other unpleasant attributes. Mr. Beddard would probably admit that the conspicuous colouring of the skunk, the coral snake, and the wasp possesses a true warning significance ; and yet he would interpret the black and yellow colouring of the larva of the cinnabar moth or the pupa of the magpie moth (both known to be unpatable) in an entirely different way, and would deny that it possesses a warning meaning.

In addition to these considerations, the undoubted existence of an unpalatable quality not residing in the superficial pigments is quite clear in many brightly coloured insects. The irritating hairs and odoriferous secretions of many Lepidopterous and Hymenopterous larva;, and the evil-smelling yellow fluids which exude from Coccincllidtr and from many conspicuous butterflies are examples.

The recent investigations of the distinguished Russian naturalist Portchinsky (II. "Coloration marquante et taches ocellees, leur origine et leur developpement," St. Petersburg, 1890) have, among other things, shown us the distinct manner in which the colours which attend unpalatability are displayed by the insect when it is disturbed. He thus explains some of the cases of "shamming death" which are so often alluded to in works on insects (the other cases being explained by the necessity for concealment). Two examples which he adduces are so interesting, and have so important a bearing on this discussion, that I cannot resist the temptation of reproducing them here, especially as Portchinsky's paper, being written in Russian, is almost unknown in this country. I have, however, been most kindly helped by my friend Mr. Morfill, and now possess a complete translation, which I hope soon to publish. The female of Spilosoma mendica possesses black and yellow legs, and, when disturbed, it folds its limbs and drops to the ground, generally (ailing on its back, so that the contrasted colours are displayed (see Fig. 1). In the closely allied Spilosoma urtica the dorsal surface of the abdomen is black and yellow, and this insect, when irritated, raises its wings and curves the abdomen downwards so that the colour is conspicuous. Furthermore,

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make trial of them upon a material which will ensure their ultimate rejection. But if the colour has not a meaning as such, there is no reason why this spot should be attacked in preference to any other part of the exposed surface; and the existence of the colour as a covering to the most vital parts seems to indicate that it acts as a warning away rather than in the reverse manner.

The fact that brightly coloured animals are frequently attacked does not seem to me to be a great difficulty. The really important point is whether the enemy remembers the attack, and is assisted in identifying the unpalatable species by its bright colours. Many experiments seem to show that this is so. Certainly Mr. Beddard will not assert that the majority of insect-eating animals fail to know and recognize a wasp without tasting it. Again, the question is really, as Mr. Titchener implies in his interesting communication, oneof "comparative palatability "; and there is no doubt that insect eating animals when sufficiently hungry will attack and sometimes devour insects which they would ordinarily reject. Furthermore, an animal which naturally prefers a varied insect food, and which is fed in c nfinement largely on other substances and partially on a monotonous insect diet, may be expected to be less scrupulous than it would be in the wild state. I may state, however, that the most intelligent insect-eating animals, such as the marmo-et, hardly ever make mistakes; their suspicion being at once aroused by any trace of a warning colour.

It is well known that we chiefly owe the theory of warning colours to Mr. A. R. Wallace. My own conviction of its entire validity rests upon the results of a prolonged series of experimenis, of which only a part has been published. I believe that I conducted these experiments fairly, that my mind was open, and that I had no personal bias in the matter at all, either in favour of or against the theory. And I can confidently make the same claim on behalf of others who have experimented in the same manner—such as Mr. Jenner Weir, Prof. Weismann, and M. Portchinsky. I may allude especially to the writings of the last-named authority, as they are the most important as well as the most recent contribution to the theory which we owe to Mr. Wallace.

1 may also take this opportunity of replying to a very similar objection raised by some reviewers against my book on the "Colours of Animals, their Meaning and Use, &c." They point out that I have not alluded to Eimer's work on the comparison of the wing markings of Papitionidtr, and they assume that his paper has, therefore, escaped my attention. But Eimer's paper has no bearing whatever on the value of colour in the struggle for existence, and this is the subject of my book, as anyone can infer from the preface, or even from the title. For this reason I was also compelled to omit reference to what I venture to regard as the far more important work of Weismann on the development of the colours and marking of caterpillars, and of Dixey on the wing-markings of Vanessidie and ArgynnidiT, as well asa very large proportion of my own work, which is a continuation of that begun by Weismann, and was, in fact, inspired by it.

Edward B. Poulton.

Oxford, December 15.

My friend Prof. Meldola has drawn my attention to a communication by Mr. K. E. Beddard in Nature of November 26 (p. 78), in which the view is expressed that the brimstone butterfly [Gonepteryx rhamm) is rendered protected or unpalatable by the yellow pigment of its wings being due to a substance formed as "a urinary pigment," and that the coloration is "a consequence of the deposition in the integument of bitter pigments."

The following objections may be urged against the view that this coloration, said to be of the nature of a "urinary pigment," affords any protection whatever.

Goncpteryx rhamni itself has its female much paler than the male and of a greenish-white hue, whilst the wings in both sexes are of a leaf-like appearance, which can only be due to the process of natural selection, and can scarcely have been exercised in the direction of "protective resemblance " if the insect was already unpalatable by the "urinative" nature of the yellow pigment of its wings.

Yellow Lepidoptera have certainly no immunity from the attacks of birds; on the contrary, the scanty records we possess of these onslaughts go to prove that the contrary is the case. The late Mr. P. H. Gosse observed one of the greenlets ( Vierosylvia calidris) to pursue a species of Terias in Jamaica ("Birds of Jamaica," p. 194). In Southern India, Mr. E. L. Arnold found the principal victims of the green bee-eaters to be specimens of Terias hecate(" On the Indian Hills," vol. i. p. 247-48). Quite recently in the Transvaal I have observed the wagtail, Motacilla capensis, to pursue and devour the yellow Lithosiid moth, Binna madagascariensis.

But the facts of " mimicry " seem to effectually dispose of the supposition. In South Africa, the yellow black-margined Papilio eenea affords by its females the most striking examples to prove the non-protective value of this coloration ; for the females respectively mimic those two well-known "protected butterflies," the blackish Amauris tcheiia and the reddish Danais chrysippus, whilst, to add to the negative evidence, the yellow male has been seen by Mr. Weale to become the prey of the flycatcher, Tchitrea cristata.

On the Amazons, Mr. Bates has long since shown that the yellow and black Leplalis arise mimics the markings—even to the colour of the antennae and the spotting of the abdomen—of the protected or unpalatable Methona psidii.

Russell Hill, Purley, Surrey. W. L. Distant.

A Difficulty in Weismannism.

In his communication of November 28 (nature, December 3, p. 102), Prof. Hartog asks us to believe that Weismann, in a letter from which he quote-, insists (1) that the Ahnenplasmas are "not completely unchangeable," and (2) that "each Ahnenplasma unit corresponds 10 an individual of the species itself: and if put under suitable trophic conditions would, singly, reproduce such an individual."

Assuming that thesis II. adequately represents the Freiburg Professor's latest views, and that a few sentences detached from their context are to be depended upon, we must, it seems tome, conclude, with Prof. Hartog, that he has unearthed an inconsistency, and, what is of more importance, shown that the shuffling process is not only unnecessary, but that a new significance must be found for it.

I am, however, still inclined to believe that hypothesis B is the one upon which Weismann has founded his theories of heredity and sexual reproduction. The hypothesis, however, should take account of the variability, slight though it may be, of the Ahnenplasmas. We agree to call the Ahnenplasmas Protozoan, simply because we have no conception of the kind and amount of the variation they have undergone since they parted company with the unicellular organisms in which they originated. We have no reason, however, ;to believe that the external causes which led to their variation in unicellular organisms are powerless to affect them now that they are localized in the reproductive cells of multicellular ones.

Prof. Hartog, moreover, while relinquishing the idea of the variability of the offspring of the lioness, endeavours from another point of view to attack Weisojannism on the plane of hypothesis B. Is he, too, sceptical as to Weismann's adherence to hypothesis A, or does he simply wish to overwhelm the >o-called disciples?

In either case, several objections may be made to his argument. In the first place, we object most emphatically to any

theory of Weismannism nu`m¢: natural selection. In the :em/rd plan, we believe that Weismann means pzrmufalians, though he uses the term combi//n/z'¢>/u. After a football team has been selected, the men can be arranged in 'll different ways. The

arrangements would virtually constitute new teams, and newspapers would speak of them as strong and weak combinations. The combinations nf the Ahnenplasmas can be assumed to be of a similar kind. The arrangement almost certainly counts for something. Nevertheless, Prof. H:1rlog’s contention-that the elimination of Ahnenplasmas in the shuffling process would lead to ever-increasing simplicity-demands serious consideration, for duplication lessens the possible number of permutations and combinations. I would point out that we may conceive that the Ahnenplasmas were, in asexual unicellular organisms, either all the mmf, all fifrml, or in intermediate conditions. In any one of these cases we must assume that m, the number of individuals, was much greater than II, the number of Ahnenplasmas present in every individual. \Vilh the evoluticn of sexuality (all the individuals being different) we should get combinations of, at least, rn Ahnenplasmas taken u at a time, Different permutations of the same combination would be, of course, possible, giving rise to other combinations, using the word in the general sense, \Ve must suppose that natural selection operated upon the variations produced by these first mmbinations. Natural selection had operated upon the unisexual ancestors of these sexual forms. We can at least conceive that development would follow one of two courses. Along the /ir.r!, combinations in which more than one unit of za kind :xppeared would, if possible, be prevented. Such might arise, but under the operation of natural selection they would not be allowed to perpetuate themselves. Along the srramf, such combinations might arise and be perpetuated. In either case, it must be a<sumed that the combinations \vhich survived were such as were best adapted to the varied combinations of external conditions. 'I`his may be made clearer by an illustration. In Rugby football, combinations of I5 in which 8 or 9 of the men-the forwards-are all the same would be strong, whereas, ifall were different, they would he weak. In Association football, strong combinations could only be made up by selecting different types of players for the difibrent places. I am inclined to believe that both cases are followed by Nature. 'I`he one which I have illustrated with reference to Rugby football cannot, however, have been generally followed. It is an adaptation for which the organism has ultimately to pay dearly, and is as dangerous to the development of the /Wy/um, as v\ e may suppose parthenogenesis to be to the Jpeczfs. Taking the case of plants, I would say that the one course may have been followed along the line of development of the main archegoniale series, the other in the development of such divergent groups as the Uslilaginen: and Gastromyceles. The argument of Prof. Hartog, therefore, while of no avail as directed against \\'eismannism, is of use in sn far as it enablesus to better understand :fir/njgfenre. I am inclined to think that it may serve also to explain the remarkable /mrsislenre of such forms as Nautilus. It suggests, loo. an explanation of the disadvantage of breeding “in and-in.” 1‘3`nal{1', I would remind Prof. Hartog that neither of the disciples of \Veismann apparently believes in the non-variability of the Ahnenplasmas. If their beliefs have asubstanlial foundation, it follows xhat the number of possible combinations becomes absolutely unthinkable. I shall be much obliged to Prof. Hartog if he can inform me of any theory of heredity whose foundations are not “ more or less mythical." There are, no doubt, many difficulties in \Veis~ mannism, before one of which, the theory, having served its time, may come lo the ground. I do not think lhat Prol I-Iartog’s is one of them. A. H. TROW. Penarlh, Cardiff December IO.

Destruction of Immature Sea Fish.

IN your number of November I9 (p. 49) you review the Ninth Annual Report ofthe Scotch Fishery Board. I have not seen the Report, but assume that your reviewer's statements as to its contents are correct. My object in writing is to draw attention tothe opinions attributed to Dr. T. \Vemyss Fulton as to the destruction of young fish by shrimpers. I may say at once that I am one of the “ very many " to whomlhe “ results " are "surprising ” as your reviewer remarks. I am an old shrimp~!rawler in the Dee and along the Flintshire coast, and I have no hesitation in saying that, as regards the Dee and, I believe, the

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Mersey and the Lancashire coast as far north as the Ribble, the destruction of young fish is absurdly under-estimated, whether I judge by my own experience or by that of Mr. R. L. Ascroft, of Lytham, with whom I have been in correspondence on the subject since 1889. This gentleman, however, informs me that Dr. Fulton's information was obtained from Morecambe Bay, where smaller trawls are used, and the boats drift with the lide instead of sailing. Dr. Fulton has Leen informed that in the Solway Firth a single boat in one year captures over II0,000 immature plaice. If the word “year " is not a mistake for "week," either the statement is immensely under-estimated or the conditions in the Solway must be very different from what they are further south. This maybe judged bythe following extract from a letter written by Mr. Ascroft in l889. I may say that this gentleman (who is now, I am glad to say, a member of the Lancashire Fishery Committee) has had a long and practical experience in all kinds of sea-fishing on the Lancashire coast, and is a careful and accurate observer. He writes as follows :-“Shrimping destroys more young (ish than almost any other agency. I have seen in Formby Channel IOCW2. of young flukes destroyed, not one the size of half-a-crown, by one boat, and there were sixty boats there that day.” Now, taking the weight of a Huke the size of hall'-a-crown at ffoz., a simple calculation will show that each boat captured 35,840 young Hukes (a term which includes plaice and dabs) in one day, or 215,040 in a week of six days-nearly twice as many as Dr. Fulton’s figures for a year! And elsewhere Mr. Ascroft says : “ You may put it as an axiom that 90 per cent. of fish that comes on a boat is destroyed, as when trawling they sail back as they have got their net, and do not commence sorting the lake until the net is out again, and they do not, in shallow water, throw the rubbish " (i.¢. everything except shrimps) “ over until they tum out to haul, for fear of getting il into the net again." All of which I may say is bome out by my own expernence. The following is an extract from my diary, written July lo, 1885, when Fishery Committees were not dreamt of. The occasion was an excursion for dredging purposes of the Chester Society of Natural Science, when I took my boat and trawl to meet their steamer at the mouth of the Dee. The Green Buoy marks lhe bar near Prestalyn, and I let down the trawl in midchannel (about 5 fathoms) in the hope of getting some natural history specimens:-“Began to trawl just below the Green Buoy. Got a fex' goodish soles, and an immense number of young soles,whic always squeeze their heads through the meshes. (N.B.-Shrimp-trawling atthistimeofyearshouldonlybeallowed within :1 quarter of a mile of the shore, to avoid the immense destruction of fry, which mostly lie further out.) Afterwards got Z1 good haul of shrimps as close in (shore) as we could go." I have a perfect recollection of the occasion, and although the trawl was only down about twenty minutes I was horrified at the number of young soles which \vere in the net, and most of which had choked themselves. Bu! there were very few shrimps, which mostly lie in very shallow water near the edge of a sand~bank. As a remedy for this destruction I would suggest that the principal breeding-grounds be ascertained, and trawling on them prohibited at such times as the young fish are there. If the prohibition be evaded, then a steamer-load of very large angular stones, distributed from |00 to 200 yards apart on the selected grounds, would effectually prevent trawling, and at the same time, as they became covered with weed, afford shelter and food to the Esh and shrimps. This has been done by Nature in this bay, where large boulders washed out of the drift that here forms the coast-line strew the shore at wide intervals, and render trawling for shrimps impossible, though hand nets can be and are worked. I trust the importance of the subject will excuse the length of this letter. ALFRED O. \VALKI-IR. Nant y Glyn, Colwyn Bay, December 14.

The Salts in Natural Waters.

Tm; inquiry of your correspondent “ R. B. H.," in NATURE of November 26 (p. 78), may be answered as follows. In the analysis of an ordinary water, after determining the respective amounts of lime, magnesia, (soda), carbonic acid (combined), sulphuric ncid, nitric acid, and chloricles (these being the constituents met with usually in such a water), we proceed to combine the acids and bases thus: the carbonic acid is calculaied to carbonate of

lime; if there be more than sufficient to satisfy all the lime, the remainder is calculated to carbonate of magnesia; if there be too little, however, the remaining lime is combined with sulphuric acid ; any remaining sulphuric acid is calculated to sulphate of magnesia, and so on ; the order in which the bases and acids are taken being therefore as follows :—

Lime, Carbonic acid,

Magnesia, Sulphuric acid,

Soda. Nitric acid.

Hydrochloric acid. Now, although this is the usually accepted and conventional method of returning an analysis, there is no doubt that the assumptions it involves are altogether arbitrary, illegitimate, and unscientific. The only scientific method of returnirg a water analysis is to represent (in parts per 100,000; not in grains per gallon, as the atrocious English system of weights and measures generally compels us to) the constituents actually found; as, for instance,

CaO; MgO; C02 ; NaO,; CI; &c.

This is all that an analyst is entitled to say, and this much is certain: when we proceed to combine the constituents, we are dealing in conjecture.

Unfortunately, however, it seems to be a "law of Nature" that those classes of the community who chiefly require the services of analysts are absolutely ignorant of the merest rudiments of chemistry; the consequence is that if any analytical purist endeavours to reform upon the conventionally established procedure, and to return a certificate of analysis in a scientific manner, his clients are up in arms at once, and indignantly demand what he means by sending them such a nonsensical rigmarole.

Thus far, then, we are helpless ; but it is most undesirable that this conventional procedure should be adhered to whenever it is possible to substitute the scientific (as in an analysis of purely scientific interest).

"R. B. H. " asks what salts really exist in solution.

According to Ostwald and others, no salts at all if the solution be dilute enough, but only dissociated ions with electrical charges. But whether this theory be correct or not, it is improbable to the last degree that an analysis represents the salts actually present. The indeterminateness of the problem is clearly shown by the fact that from the same solution either sodium chloride and magnesium sulphate, or sodium sulphate and magnesium chloride, may be obtained, according to the method of crystallization adopted. Even supposing that Ostwald's theory be incorrect, and that not ions but salts exist in solution, and that these different results be due to double decomposition occurring in one case, it would be a gigantic assumption that we 'can definitely show the exact natural distribution in a complicated solution containing eight or ten constituents.

If "R. B. H." wishes to see an account of how acids and bases distribute themselves in a simple solution, he may consult Ostwald's "Outlines " (p. 338, &c English translation), and also the discussion on avidity in Lothair Meyer's "Modern Theories of Chemistry" (472-87). F. H. Perry Coste,

7 Fowkes Buildings, Great Tower St., E.C., Nov. 28.

I AM much indebted to Mr. Perry Coste for his clear and candid answer to my question. It is exactly the answer which I anticipated. The actual facts established by analysis are too often forced, by the arbitrary assumptions of the analytical chemist, to yield unwarrantable conclusions.

The reason given is, that "the people love to have it so." I had hoped that chemists could give some better grounds for their proceedings. They bring to mind the words of the old prophet. "A wonderful and horrible thing is come to pass in the land -, the prophets prophesy falsely," ... for "my people love to have it so ; and what will ye do in the end thereof?" Surely we may henceforth claim, in the interests of truth or (which is the same thing) science, that chemists will give us in every case the actual facts obtained by analysis ; and if they proceed further for the sake of the prejudices of the ignorant, they will at least warn them that such further inferences are not trustworthy, and have only a very moderate amount of probability, if they can even lay claim to any probability at all.

I speak feelingly, because I have had occasion to examine a great number of analyses of water from the chalk of the London Basin, telling me, in most cases with a " cocksureness" which has amazed me, what salts, and what amount of them, these waters contained, and these, for purposes of comparison, I have

had painfully to reduce back to the real facts from which they were derived.

I am quite prepared to believe that the investigations of Ostwald and others as to solutions show that salts as such do not exist in these waters at all, and that the relations of acids and bases in such cases are variable with the physical condition of the water. As an instance which has come under my own notice, it was reported by competent chemists, with reference to water from a deep well in Harrow, in which an unusual quantity of magnesium and sulphuric acid was found, that at 60° F. its hardness was lo°'4 (grs. per gall.); that, mixed with an equal quantity of distilled water, its hardness rose to 240: while at the temperature of 158° it rose to 26°'S. I suppose that a chemist would hardly attempt to assign with much confidence what exact changes in the relations of the dissolved constituents would produce these and similar results. All the more reason, then, why analysts should limit themselves to statements which they can vouch for by direct observation and the balance.

My remarks having extended beyond a mere question, I think it best to sign myself in full, Robert B. Hayward.

Peculiar Eyes.

Mr. Shaw's case is by no means so peculiar as he supposes. I imagine that everyone who has had to do with experimental questions of physiological or psychological optics has found it to be rather the exception than the rule that an investigation of his reagents' eyes has shown their perfect equality—as regards "long" and "short" sight, colour sensitivity, and sensitivity to light. The common preferential use of one eye explains a good deal (cf., e.g., Aubert, "Physiol, d. Netzhaut," p. 18; Schon, Arch. f. Ophthalmologic, xx. 2, p. 271). Mr. Shaw may also be colour-blind in one eye; the perception of colour difference alone is no criterion. I find it safest to employ the wool, spectrum, and coloured-card tests in combination.

Animals (with the exception of the very highest) have normally a so restricted binocular vision that they need not be taken into account.

It may be interesting to note that a like difference of sensational capacity exists between the two ears. A tuning-fork held to one ear may, quite normally, drown a tone-sensation which is half a musical tone deeper or higher than that excited by the same fork in the other ear. E. B. Titchener.

P.S.—I discovered the very considerable inequality of my own eyes quite accidentally in my sixteenth year.

Alleged Pseudopodes of Diatoms. Will you allow me to express my concurrence in your criticism (p. 140) on Mr. Grenfell's paper on the occurrence of pseudopodia in the Diatomaceous genera Melosira and Cycletella? I express no doubt on the accuracy of Mr. Grenfell's observations, the knowledge of which I have derived from his paper in the Quarterly Journal of Microscopical Science, and from his verbal description at a meeting of the Linnean Society; but I do desire to enter my protest against the use of the term "pseudopodia" for the protoplasmic filaments observed by him. According to the accepted meaning of this term, it is applied to masses of protopUsm which are in organic connection with the protoplasm of the body of the organism, and which are retractile. I understand Mr. Grenfell that he is unable to affirm either of these facts with regard to the structures observed by hiui; and, until this is done, the application to hem of the term "pseudopodia " appears to me to involve a begging of the question at issue, and a needless and regrettable confusion in terminology. Alfred W. Bennett.

Intelligence in Birds.

Under this head Mr. Wilkins, in your last impression (p. 151), speaks of Podoces t>an,rri hiding food in the sand. I have a fox-terrier puppy which was taken from its mother when about seven weeks old, and sent to me. I have no other dogs, nor has he seen any dogs, but he buries bones in the garden with great skill, digging a hole with his fore-paws. He puts in the bone, and carefully pushes it down with his nose, and then covers it with garden soil, which is pushed in with his nose. The work is very carefully and elaborately well done.

I have had, at various times, very many dugs of all kinds and ages, but I never saw so young n puppy bury bones, or .iny dog do it so well. It is an admirable example of pure heredity.

Norfolk Street December 19. Joe.

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from a prospector in Arizona informing them he had found a vein of metallic iron near Canon Diablo, and sending them at the same time a piece with the request for an assay. Some time in April this piece was exa

sent to the President ot the Santa Fe Railroad, and another to General Williamson, the Land Commissioner of the Atlantic and Pacific Railroad Company, in Chicago,

1 Read before the American Association for the Advancement of Science, by A. E. Foo'c-, August 20. 1891. From the American Journal of SeUnce and Arts for November 1801.

1 This assay was of such a remarkable character that I took the trouble to stop at the city where it was made, and ask how such extraordinary results were obtained. I was informed that the lead, silver, and gold were probably the results of the materials used in making the assay.

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