july 1899] I. W. HEADLEY ON EVOLUTION 47 



replies that they are modified by the changes in their nutritive pro- 

 cesses, which are affected by changes in their circumstances ; and it 

 does not seem to have occurred to him that such changes might be as 

 well supposed to take place among animals." That plants cannot be 

 said to have wants is rather a strange assertion from a scientist of 

 Huxley's eminence, and the statement that it did not occur to Lamarck 

 that changes in animals take place through their nutritive processes, as 

 he alleges they do as regards plants, is a deplorable bit of gratuitous 

 imputation for a great reasoner like Huxley to make, seeing that 

 Lamarck was continually reiterating that fact. For certainly Lamarck's 

 " wants " include the want of food, and if circumstances force animals 

 to modify their method of feeding, a new habit will or may be con- 

 tracted, leading gradually through heredity to modification of organs. 

 Again, we see the misinterpretation of Lamarck in Mr. Herbert Spencer's 

 "Principles of Biology," when he implies that the idea as to what 

 induces organic change in the theories of Erasmus Darwin and 

 especially Lamarck, is identical or very similar to the motive force 

 implied in " Vestiges of Creation " and Prof. Owen's works whereas 

 there is no real likeness, or, in fact, no more than is between the 

 vitalist's theory of life and that of the physicists. 



I agree entirely with Mr. Headley when he states that the guiding 

 principle of evolution must be sought for in the organism itself; for 

 that is what Lamarck ever maintained. Again, Mr. Headley states 

 that the paths open in the evolution of species are limited. That is 

 also true, and for the simple reason that they must follow the lines 

 of function. Take up any work on physiology, and we soon learn 

 why the paths of evolution are limited, for organic life depends on 

 only a few great functions, viz., nutrition, including respiration, repro- 

 duction, and locomotion, all governed by the nervous system, and hence 

 it must be on these lines — the great vital functions, as distinct from 

 the special organic functions — that evolutionary changes are brought 

 about when changes in environment lead to change in organic reaction 

 in the formation of new species. 



It seems to me we should look at organic matter as a condition of 

 energy, i.e., as, in a highly plastic state, capable of being modified either 

 directly or indirectly according to the exigencies of the organism. 

 Weismann now admits (a modification of his former views) that varia- 

 tions are caused by the reaction of the germinal protoplasm to 

 extrinsic forces. But why does he not see that this reaction to 

 extrinsic forces is not limited to embryonic life, but is continuous during 

 the whole life of the organism, from inception of life to death, gradually 

 decreasing, of course, in inverse ratio with the duration of life of the 

 organism. We should thus be able to account not only for variations 

 appearing at birth, but also for the inheritance of functionally -produced 

 modifications. 



That the course of organic evolution is gradual — one step in a 



