542 CLAEENCE E. McCLUNG 



('02, '05), and the case is supported by observations of Sinety 

 ('01) and others. In this instance an element, so well marked 

 by peculiarities of form and behavior as to be unmistakable in 

 every cell generation, is found to be united to one of the eucliro- 

 mosomes at all times so as permanently to reduce the haploid 

 number to eleven. There is actuall}^ one less free and inde- 

 pendent chromosome in cells of these animals than in those of 

 other members of the group. This however is a far different 

 thing from saying that there is one less chromosome present. 

 In fact there is no difference at all in the number of chromo- 

 somes — the sole variation being the union of the accessory chro- 

 mosome with one euchromosome. To put the case thus is to 

 make a plain statement of fact and not to create an hypothesis. 

 The apparently missing element is just as clearly present as in 

 any other Orthopteran cells. Irrefutable proof is thus afforded 

 of the process of the fusion of chromosomes without loss of their 

 identity. As a principle of nuclear organization we have there- 

 fore to reckon with the ability of chromosomes to unite together 

 while still retaining their morphological integrity. 



It is also conceivable that where a tendency of this kind mani- 

 fests itself between certain chromosomes in a species, it may 

 also obtain between other members of the complex. Such com- 

 binations are more difficult to detect on internal structural evi- 

 dence, because there is no such differential behavior as charac- 

 terizes the accessory chromosome. Nevertheless there are valid 

 criteria which may be employed and these make certain the 

 existence of such multiple chromosomes. The conditions dis- 

 played in H. vu-idis are peculiarly fortunate and may now be, 

 considered in detail. From the study of thirty-eight individuals 

 of H. viridis it is apparent that (a) the number of chromosomes 

 in the first spermatocyte may vary from nine to thirteen and 

 that (6) the same number may be present in two or three indi- 

 viduals and 3^et in each case be differently constituted. The 

 necessity for a careful and detailed study of the complex before 

 passing judgment upon the significance of numerical variation, 

 is certainly apparent from these circumstances. In view of the 

 fact that most explanations' of changes in the number of chromo- 

 somes have concerned the smaller members of the series, it is of 



