Resident's address!. 17 



«,iiulogy is liDi bxuiSl, but such au imaginary caso is at least 6i ii diti'ereiiL 

 type from a change in habit consisting in the addition o£ a new link or 

 the alteration of one of the latest formed links. If we were as ignorant 

 of the growth of human actions as we are of variation, we might have a 

 school of naturalists asserting that all changes in habit originate in the 

 earliest link of the series. But we know that this is not the case. On the 

 other hand, I fully admit that the structure of an ovum may in this way 

 be altered, and give rise to a variation which may be the starting-point of 

 a new species. 



But how can a new species originate according to an epigenetic theory ? 

 How can a change in the latter stages of ontogeny produce a permanent 

 alteration in the germ-cells t Our answer to this question will depend on 

 our views of the structure of the germ-cella. According to the mnemic 

 theory they have the quality which is found in the highest perfection 

 in nerve-cells, but is at the same time a character of all living matter — ■ 

 namely, the power of retaining the residual effects of former stimuli and 

 of giving forth or reproducing under certain conditions an echo of the 

 original stimulus. In Semon's phraseology germ-cells must, like nerve-cells, 

 contain engrams, and these engrams must be (like nerve-engrams) bonded 

 together by association, so that they come into action one after another in 

 a certain order automatically, i.e., in the absence of the original stimuli. 



This seems to me the strength of the mnemic theory — namely, that it 

 accounts for the preformed character of germ- cells by the building up in 

 them of an organised series of engrams. But if this view has its strength, 

 it has also its weakness. Routine can only be built up by repetition, but 

 each stage in ontogeny occurs only once in a lifetime. Therefore if 

 ontogeny is a routine each generation must be mnemically connected 

 with the next. This can only be possible if the germ -cells are, as it 

 were, in telegraphic communication with the whole body of the organism ; 

 so that as ontogeny is changed by the addition of new characters, now 

 engrams are added to the germ-cell. 



Thus in fact the mnemic theory of development depends on tho 

 possibility of what is known as somatic inheritance or the inheritance 

 of acquired characters. This is obvious to all those familiar with tlic 

 subject, but to others it may not be so dear. Somatic inheritance is 

 popularly interesting in relation to the possible inherited effects of educa- 

 tion, or of mutilations, or of the effects of use and disuse. It is forgotteii 

 that it may be, as I Iiave tried to show, an integral part of all evolutionary 

 development. 



WeismcDitis Theory. 



Everyone must allow that if Weismann's theory of inheritance is 

 accepted we cannot admit the possibility of somatic inheritance. This 

 may be made clear to those unfamiliar with the subject by an illusti-atiou 

 taken from the economy of an ant's nest or beehive. The queen ' on 



' Nor do the drones share the activity of tlie workers. 

 1908. c 



