33O W. E. HOY, JR. 



type with those of the germ cells. Apparently any peculiar 

 history of the chromosomes in somatic cells must be regarded 

 as a concomitant of differentiation. This atypical "behavior" 

 of the chromosomes, in lieu of a better explanation, has been 

 satisfactorily accounted for from the standpoint of the doctrine 

 of the "individuality" of the chromosomes in the following 

 manner: in those forms where the chromosomes exist in the 

 somatic cells in greater number than in the germ cells, investi- 

 gators generally agree that the chromosomes of the sex cells 

 are bivalent or plurivalent. These chromosomes fragment prob- 

 ably quite early in the development of the embryo, as has been 

 shown in the case of Ascaris and that of the Hymenoptera. Con- 

 versely, where the number of the somatic chromosomes is lower 

 than the number of the chromosomes in the sex cells, there is a 

 more or less permanent pairing or fusion of the chromosomes in 

 the soma. 



Accordingly the behavior of the chromosomes in the soma can 

 be tentatively summarized in the following manner: 



1. All of the chromosomes in the gametes are univalent, and 

 are of the same number and type in all the cells of the body, 

 both somatic and germinal. 



2. The chromosomes of either one or both of the gametes are 

 compound, and in one of the early cleavages of the egg fragment 

 into their component parts in the cells giving rise to the soma. 

 This procedure clearly distinguishes the Keimbahn from the soma 

 by establishing a dissimilarity between the two in the number 

 and type of their chromosomes. 



3. The production of double or multiple chromosome groups 

 by the suppression of cell division. 



4. All of the chromosomes of both gametes are univalent, 

 but become bivalent in the cells of the soma by a more or less 

 permanent fusion with other chromosomes. The resulting chro- 

 mosomes appear univalent. 



A consideration of this problem will tend to strengthen the 

 view that the chromosomes, to a certain degree at least, are 

 constant and not variable structures, and that they possess a 

 certain morphological identity in the majority of animals. In 

 the case of Anasa, with which this paper deals, there are certain 



