770 PROCEEDINGS OF SECTION J. 
heredity, 3 nel ee divide Le who have taken part in 
«The first compris es an ais rami whether on philo- 
sophical or on scientific grounds, the theory of the gradual 
transmission, from generation to generation, of characters 
acquired in the lives of individuals. The philosophy of ~ 
Herbert Spencer, who adopted this theory from Lamarck in 
pre-Darwinian days, is saturated with it. Haeckel, too, has 
nailed his colours to the mast, affirming that “ the inherit- 
ance of characters acquired during the life of the individual 
is an indispensable axiom of the monistic doctrine of evolu- 
tion.”’ The acquired characters here spoken of include those 
resulting from use or disuse.* 
A second class is composed of those who- believe, with 
Weismann and Wallace, that there is no evidence of such 
transmission. Darwin, while accepting the transmission of 
variations resulting from use and disuse, saw that, if true, it 
would account only for a small part of the facts. His 
theory of natural selection was satisfied with the truth that 
variations do make their appearance in the course of descent, 
no individual being exactly like another; and he showed 
how these variations were naturally eliminated if prejudicial, 
or conserved if beneficial, thus giving rise to new species. 
The ulterior question—whence the variations?—though by 
no means neglected by Darwin, lay beyond the limits of his 
special inquiry. Neo-Darwinians call attention more 
emphatically to his theories of natural and sexual selection, 
leaving the original variations to be accounted for in other 
ways. One of the latest utterances on this question is by 
Professor Ewart, in his address as President of the section of 
Zoology at last meeting of.the British Association. He lays 
stress on maturity, habitat, nutrition, and temperature, as 
causes of variation; but does not believe there is any trust- 
worthy evidence that definite somatic variations are incor- 
porated in the germ-cells and transmitted to offspring. The 
general tendency of recent thought has undoubtedly been to 
diminish the importance formerly attached to the doctrine 
of use-inheritance. 
In a third or intermediate class may be placed those who 
do not reject the transmission theory in toto. They retain 
it as a provisional or working hypothesis, using it in cases 
where other explanations are not readily forthcoming, or 
appear to be unsatisfactory. Further light will doubtless — 
be thrown on the subject by experiments which are now 
being conducted on plants and on some of the lower forms 
of animal life. 
