574 CLARENCE E. McCLUNG 



for its specific individuality. That this distribution is properly 

 maintained, although the element is no longer free in the mul- 

 tiples, is only another confirmation of the conclusions otherwise 

 determined. 



Another evidence of specific organization through acts of dis- 

 tribution comes from the studies, upon unequal and hetero- 

 morphic chromosom£S by Miss Carothers ('17). Organization, 

 expressed in size or form, is perpetuated by a distribution and a 

 conceivable recombination according to chance movements. 

 There is no indication that any indefinite variation exists. 

 While it is true that no explanation of the origin of the hetero- 

 morphic condition is strongly suggested by the facts so far ob- 

 served, it may be noted that Wenrich's work affords objective 

 evidence regarding inequalities in size. Always a means for 

 the maintenance of given conditions appears in the mechanism 

 of mitotic distribution. 



The same precision in distribution which marks the accessory 

 chromosome is true also of the elements which unite to form the 

 euchromosome multiples. No difference exists between the 

 distribution of these members of the complex, whether free or 

 combined. It might be thought that the intimate and appar- 

 ently permanent association of two chromosomes^ resulting in 

 the formation of a new mitotic unit of different value, would ma- 

 teriall}' change the activities of the components. So far as I 

 can see this is not the case, and even the details of movements 

 in the prophase are preserved in the face of the multiple 

 condition. 



The problem of accounting for the occurrence of a given vari- 

 able series of heteromorphic chromosome combinations in 

 Trimerotropis has been considered by Miss Carothers and she 

 properly arrives at the conclusion that segregation and chance 

 recombination of components offer a competent explanation of 

 the observed phenomena. At the same time ihere is not ex- 

 cluded the possibility of a readjustment of relations between the 

 chromosome complex and the new cytosome at the time of fer- 

 tilization, which, within a limited range of possibilities, would 

 result in a similar variable series. The conditions mthin the 



