622 APPENDIX B. 



This very pronounced opinion will be met, on the part of some, 

 by a no less pronounced demurrer, which involves a denial of 

 possibility. It has been of late asserted, and by many believed, 

 that inheritance of acquired characters cannot occur. Weismann, 

 they say, has shown that there is early established in the evolu- 

 tion of each organism such a distinctness between those compo- 

 nent units which carry on the individual life and those which are 

 devoted to maintenance of the species, that changes in the one 

 cannot affect the other. We will look closely into his doctrine. 



Basing his argument on the principle of the physiological 

 division of labour, and assuming that the primary division of 

 labour is that between such part of an organism as carries on 

 individual life and such part as is reserved for the production of 

 other lives, Weismann, starting with " the first multicellular 

 organism," says that " Hence the single group would come to 

 be divided into two groups of cells, which may be called somatic 

 and reproductive the cells of the body as opposed to those 

 which are concerned with reproduction." (Essays upon Heredity, 

 i, p. 27.) 



Though he admits that this differentiation " was not at first 

 absolute, and indeed is not always so to-day," yet he holds that 

 the differentiation eventually becomes absolute in the sense that 

 the somatic cells, or those which compose the body at large, come 

 to have only a limited power of cell-division, instead of an un- 

 limited power which the reproductive cells have ; and also in 

 the sense that eventually there ceases to be any communication 

 between the two further than that implied by the supplying of 

 nutriment to the reproductive cells by the somatic cells. The 

 outcome of this argument is that, in the absence of communica- 

 tion, changes induced in the somatic cells, constituting the indi- 

 vidual, cannot influence the natures of the reproductive cells, and 

 cannot therefore be transmitted to posterity. Such is the theory. 

 Now let us look at a few facts some familiar, some unfamiliar. 



His investigations led Pasteur to the positive conclusion that 

 the silkworm diseases are inherited. The transmission from 

 parent to offspring resulted, not through any contamination of 

 the surface of the egg by the body of the parent while being 

 deposited, but resulted from infection of the egg itself intrusion 

 of the parasitic organism. Generalized observations concerning 

 the disease called pebrine, enabled him to decide, by inspection of 

 the eggs, which were infected and which were not : certain modi- 

 fications of form distinguishing the diseased ones. More than 

 this ; the infection was proved by microscopical examination of 

 the contents of the egg ; in proof of which he quotes as follows 

 from Dr. Carlo Vittadini : 



" II r6sulte dc mes recherches sur Ics graincs, i I'e'poquc ou commence le 



