IIS 



THE AMERICAN NATURALIST [Vol. XLIV 



are not at all inconsistent with the idea that melanin formation 

 is in itself a generalized function of the cell. Cytological in- 

 vestigations during the past two or three decades lend support 

 to the hypothesis that the cell is composed of a number of more 

 or less definite organisms. Now the production of black pig- 

 ment, for instance, may be a process in which every organ of the 

 cell plays a part. Kiddle lias shown that the particular color 

 of an organism, when this color is melanic in character, is due 



definite point. We may imagine that the relative quantity of 

 tyrosin and tyrosinase present in the cell has something to do 

 with the point at which the process terminates under normal 

 conditions. Now if a single cell organ should, because of some 

 change in its nature, fail to produce its usual measure of one 

 of these necessary substances, we may easily imagine that the 

 point at which the oxidation process would stop would be 

 changed accordingly. Now if the cell organ which is respon- 

 sible for this difference happens to be a chromosome, and if 

 chromosomes behave in the reduction division as a great many 



further developed i 



Riddle continually draws con 

 justified by the facts he states, 

 melanin formations, under certg 

 dieate that for the building of 

 conditions of the organism or th 



the shuffling of color factors thr< 

 necessary conclusion unless we t 

 organs in the cell. I have just 

 been calling factors may really be 

 of cell organs. There 



horns of cattle are a j 

 organs develop only at 

 tendency to develop the 



