582 CLARENCE E. McCLUNG 



differs from time to time, movements of parts take place, frag- 

 mentation occurs, extreme attenuation or extension of substance 

 is found, even separation and recombination of parts may 

 happen and yet the individual maintains itself. What it may 

 have been in the past, what its possibilities of future develop- 

 ment are, what potentialities of multiplied individuality it 

 suppresses do not affect the reality of its individuality. It is, 

 as Huxley says, "a single thing of a given kind." If one such 

 thing divides into two, there are two individuals; if two unite 

 into one indistinguishably there is a single individual; if a 

 fusion of two things occurs in part, without loss of physical 

 configuration, there are still two individuals in existence. Only 

 when the substance of one thing disappears or becomes incor- 

 porated integrally into the organization of another does its 

 individuality depart. 



If all these variations of physical state may occur in the his- 

 tory of an organism without sacrifice of individuality, there can 

 be no reason for urging them against a conception of the indi- 

 viduality of the self perpetuating chromosomes. Especially is 

 this true in face of the facts recorded here and in other papers 

 showing the high degree of chromosome constancy, for any given 

 period, in all the attributes by which we usually judge indi- 

 viduality. The conditions in Hesperotetix and Mermiria at 

 first seem to be a contradiction to this generalization, but, when 

 examined with care, show, not an instance of fundamental 

 change, but merely of modified detail. From these results it is 

 very clear that a chromosome number less than normal for the 

 group is not a necessary evidence of lost elements. In a similar 

 manner the studies of Miss Holt on the intestinal cells of Culex 

 indicate definitely that numbers in excess of the normal do not 

 signify the addition of anything not previously represented. 

 Loss or gain in chromosome numbers is a condition to be inves- 

 tigated, not implicit evidence of an altered organization with 

 loss of organic individualities. That the chromosomes are not 

 the ultimate structural units is, however, indicated in many 

 ways, but it remained for Wenrich to show the nature of this 

 more minute portion of the chromosome architecture. From 



