JULY 1899] fF. 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, 1.¢., a8, 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 
