No. 524] CHROMOSOMES AND HEREDITY 



477 



Moreover, there is no evidence that color production is 

 less intense here. 



The other alternative can be answered on more general 

 grounds. If Mendelian characters are due to the pres- 

 ence or absence of a specific chromosome, as Sutton's 

 hypothesis assumes, how can we account for the fact that 

 the tissues and organs of an animal differ from each 

 other when they all contain the same chromosome com- 

 plex. Bateson has called attention to this weakn<^> of 

 the single-chromosome-single-character hypothesis. For 

 on such a view the chromosomes should be sorted out in 

 the soma until each region gets its proper kind. The 

 facts are the reverse. However important therefore the 

 chromosomes are in transmitting the full quota of heredi- 

 tary traits, we must he prepared to admit that the evi- 

 dence is entirely in favor of the view that the differentia- 

 tion of the body is due to other factors that modify the 

 cells in one way or in another. This consideration is, to 

 my mind, a convincing proof that we have to deal with 

 two sets of factors — the common inheritance of all the 

 cells to produce all the kinds of tissues and organs in the 

 body, and the limitation of that property in the course 

 of development. If the former is due to the chromo- 

 somes and the unspecialized parts of the cytoplasm, the 

 latter may be due to the local changes that the relation 

 of the parts to each other calls forth. It might even 

 be argued that since in the development we find no evi- 

 dence of a sorting out of the chromosomes that produce 

 special parts, the individual chromosomes can not stand 

 each as the representative of those parts, but rather that 

 each part needs the entire set of chromosomes for its 

 normal life. However tempting such an argument may 



the possibilities of chromosomal behavior to make this 



be for those who have r» 

 elusion that this is the 

 the chromosomes, the a 



s argument will not appear conclu- 

 aot accept such a general standpoint, 

 claim that we know too little about 



