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pally found amongst the plants of tropical regions, especially amongst Dicotyledons with a gamopetalous corolla and inferior ovary, such as the Compositæ, Dipsaceæ, Campanulaceæ, &c., and, amongst other flowering plants, those with a specially complicated organization, such as Orchids, Palms, Apocineæ, Asclepiads, Cucurbitaceæ, Passionflowers, Begonias, &c.,”-in fact, if we suppose the most ancient to be those with the least, and the most recent those with the most highly specialized parts. Mr. Bentham, one of the most learned and cautious naturalists, holds precisely similar views; and no one is more eminently fitted to form a conclusion.

The facts themselves on which these great naturalists have founded their opinions are too numerous and complicated to be given here ; this is sufficiently proved by the size of M. De Candolle's work on the geographical distribution of plants, which consists of 1350 closely printed pages.






Our present knowledge only permits us to speak with great caution with regard to the evolution of organic from inorganic matter. There is, however, much indirect evidence to justify a belief that it had such an origin ; and this is important, since if it could be proved that organic matter had a separate origin from inorganic, it would be reasonable to believe in the separate origin of its various modifications.

Many experiments have been made with a view to prove that living things may originate de novo in various organic and inorganic solutions; and the hypothesis of spontaneous generation has been advocated by some, although it is indubitable that the weight of evidence has hitherto been in favour of the doctrine that no living thing can originate without the admission of living germs or seeds*.

* A careful perusal of Dr. C. Bastian's work on the Beginnings of Life' has failed to change the author's opinion on this point.

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It is by no means, however, to be concluded on this account that living matter will never be artificially produced; for it will be seen in the sequel that the development of organisms and structure is probably a far more complex phenomenon than the production of mere structureless material capable of undergoing organization. Indeed we may confidently anticipate that such material will eventually be formed, just as sugar, alcohol, valerianic acid, and a multitude of similar organic bodies have been formed by the chemist, which were formerly believed never to originate except by the action of vitality.

Such structureless organic matter is called Protoplasm. It may fairly be looked upon as the basis from which all living creatures have arisen. Each individual is at first a mere speck of protoplasm; and the simplest forms of life retain that form throughout their whole term of existence. The most complex animal or plant consists of a mere aggregation of such minute particles variously bound together : of these some retain their primitive structureless condition, as “wandercells” and white blood-corpuscles; and others undergo changes which alter their appearance, so that they are only recognized when their development has been carefully studied.

Protoplasm is a viscid structureless colloid, per



meated by crystalloid atoms. It is very unstable in its composition, and contains the element nitrogen. It is capable of transforming energy, derived either directly or indirectly from the rays of the sun, into molecular forces, thus delaying its dissipation as radiant heat. The forces which originate in this manner, either produce movements of the mass or determine the formation of structure ; they also enable it to assimilate suitable material to itself, so that its mass increases or grows. So long as these phenomena continue, it is said to live. Unless it is continually supplied with both energy and material, it soon undergoes such chemical changes that it becomes incapable of transforming energy: it is then said to die. It may, however, retain its properties indefinitely under certain conditions, when neither energy or material are supplied, if all chemical change be arrested, as by desiccation or freezing ; its life is then said to be dormant.

There can be no question that protoplasm differs from all other kinds of material in the possession of certain well-marked properties, which have been enumerated above; but the same may be said of every substance in nature which has striking peculiarities. Ammonia, chloride of silver, or iron may each be said to differ as strikingly from all other kinds of matter, or at least from each other.



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Although no other substance possesses all the properties of protoplasm, yet it may be confidently affirmed that none are entirely peculiar to it.

Its heterogeneous nature, partly colloid and partly crystalloid, as well as its unstable composition, may be passed over without comment; but its influence on energy requires careful consideration.

When light falls upon a surface it is either reflected, transmitted, or absorbed. In the latter case it disappears as light, its vibrations being transformed into heat. Whether this heat arises from work done in the body by the light-vibrations, or whether it is the direct result of the impact of the vibrations of light, has not been determined ; but in the majority of inorganic bodies no apparent change results, even when the action of light is prolonged for a considerable time. In some cases, however, we have abundant evidence of molecular work being performed by the impact of lightvibrations. This is well seen in the processes of photography and bleaching. Light acts as a powerful deoxidizer, and is extremely energetic in its effects on certain salts. It is also capable of giving rise to rapid chemical combination, as, for instance, when it falls upon a mixture of chlorine and hydrogen gas. When light falls upon vegetable protoplasm, its energy is applied to the de

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