A CRITICAL EXAMINATION 33 



cates that the chromosomes are directly and pri- 

 marily concerned in the distribution and trans- 

 mission of hereditary differences. This does not 

 mean, however, that one can unreservedly assert 

 that the chromosomes are the exclusive agents in 

 hereditary determination. On the contrary, there 

 are a number of facts recorded in the literature of 

 cytology which, in the light of present knowledge, 

 can only with great difficulty, if at all, be recon- 

 ciled with such a view. In this connection it 

 should be pointed out that the most acute and 

 philosophical students in this field no longer re- 

 gard the determination of hereditary specificities 

 as probably confined exclusively to a single mor- 

 phological element of the cell. Thus Wilson z has 

 recently said: "In any case, the conclusion is 

 not to be escaped, I think, that the whole cell 

 system is directly or indirectly involved in the 

 production of every hereditary trait. To treat 

 the chromosomes as if they were central governing 

 or controlling factors in the cell is a procedure of 

 more than doubtful expediency. For the present, 

 at least, all the requirements of investigation are 

 sufficiently met if we think of the chromosomes, 

 or that which they carry, only as differential factors 

 in heredity, not as its primary or exclusive * de- 

 terminers.' Whether they possess a significance 

 more fundamental than this is a question that may 



1 Wilson, E. B. "Heredity and Microscopical Research." Science, 

 N. S., Vol. 37, pp. 814-826, 1913. 



D 



