Without the idea of spontaneous generation and a physical theory of life, the doctrine of evolution is a mutilated hypothesis without unity or cohesion. On this point Lamarck speaks most clearly: "Although it is customary when one speaks of the members of the animal or vegetable kingdom to call them products of nature, it appears that no definite conception is attached to the expression. Our preconceived notions hinder us from recognising the fact that Nature herself possesses all the faculties and all the means of producing living beings in any variety. She is able to vary, very slowly but without cessation, all the different races and all the different forms of life, and to maintain the general order which we see in all her works."
The doctrine of Lamarck is frequently misinterpreted. We often hear it expressed as "Function makes the organ," or even "Function creates the organ." This is equivalent to saying, "Life makes the living being," which is incomprehensible, { 165} making of function a sort of immaterial and independent entity which constructs a material organ in order to lodge within it. No such idea is to be found in all the works of Lamarck. He formulates his law in the following terms: "In every animal which is still undergoing development, the frequent and sustained use of any one organ increases its size and power, whereas the constant neglect of the use of such organ weakens and deteriorates it, so that it finally disappears."
In his expression of this law Lamarck insists on the fact that organization precedes function. He affirms only that function, _i.e._ action and reaction, modifies the organ; or, in other words, that organisms are modelled by the action of exterior forces acting upon them. It is in this sense only that function may be said to make an organ, but this mode of expression should be avoided, as it is apt to be misunderstood.
Astronomy teaches us that our globe was detached from the sun in an incandescent state, and geology asserts that this earth has passed through a period of long ages when its temperature was incompatible with the existence of life. It was only with the cooling of the earth crust that it was possible for living beings to make their appearance. Hence they must of necessity have been produced spontaneously from terrestrial material under the influences of chemical and physical forces. This opinion imposes itself on all who reflect and judge freely. In the same way the doctrine of evolution necessitates as a corollary the doctrine of spontaneous generation. The doctrine of evolution should reconstitute every link in the chain of beings from the simplest to the most complicated; it cannot afford to leave out the most important of all, viz. the missing link between the inorganic and the organic kingdoms. If there is a chain, it must be continuous in all its parts, there can be no solution of continuity.