84 'DETERMINANTS' VERSUS 



plicated branched nuclei and then adds, quite irrespectively of 

 any theory, " It seems noteworthy that it is the nuclei of secret- 

 ing cells, i.e., cells characterised by lively activity in which the 

 principle of surface enlargement by branching is especially 

 expressed." 



There seems to be no definite way for reconciling this view as to 

 the function of chromatin with the other view more commonly 

 received, that it is the bearer of hereditary traits ; though it may 

 be said that this second function is not necessarily in conflict with 

 the first. " While the unstable units of chromatin, ever under- 

 going changes, diffuse energy around, they may also be units which, 

 under the conditions furnished by fertilisation, gravitate towards the 

 organisation of the species. Possibly it may be that the complex 

 combination of pi'oteids, common to chromatin and cytoplasm, is the 

 part in which the constitutional characters inhere ; while the 

 phosphorised component, falling from its unstable union and 

 decomposing, evolves the energy which, ordinarily the cause 

 of changes, now excites the more active changes following 

 fertilisation." 



We are here indeed introduced to a question which some of the 

 most recent experiments on ' merotomy ' have again brought 

 forward : namely, whether experimental evidence does not show 

 that hereditary traits may inhere in the cytoplasm as well as in the 

 nucleus. Thus, in the third of an important short course of lectures 

 recently delivered by Prof. Weldon at University College he is 

 reported to have said,' " The nucleus has been held to be the sole 

 vehicle of heredity by Weismann. Recent experiments of Boveri 

 and Delage have demonstrated that this is incorrect. Both these 

 writers have shown that denucleated eggs, produced by mechanical 

 extrusion of nuclei, can be fertilised in the sea-urchin, and that they 

 give rise to normal blastulas, gastrulae and larvae. Hence the 

 ' determinants ' of heredity are present in the cell body of the egg. 

 If such eggs are fertilised by alien spermatozoa (of different sub- 

 species) the larva shows the characters of the male parent, because 

 the determinants of these are more potent." 



Exception was subsequently taken to this statement ("Lancet," 

 Feb. i8th, p. 460), which seems to have been not quite sufficiently 

 guarded, judging from the comment appended to the objection 

 which was as follows : — " Boveri himself admits that the ' merogonie ' ' 



» " The Lancet," Feb. 4, 1905, p. 308. = A synonym for ' merotomy.' 



