MULTIPLE CHROMOSOMES 535 



has separated from its V-homologue to which it was joined in 

 synapsis. The only differences between Mermiria and most 

 other Orthoptera are (a) the multiple chromosome V and (b) the 

 euchromosome V. That the union of the accessory to a euchro- 

 mosome is not a fundamental change of the nuclear state is in- 

 dicated by the fact that certain species of Mermiria lack the 

 association. No change in the distribution of the accessory re- 

 sults from its union, and, as we have seen in Hesperotettix 

 viridis, the combination may be so weak as not to occur in some 

 individuals. 



Evidence that the euchromosome V is of like transitional 

 character is not wanting in certain well marked members of this 

 loosely constituted species. In these (figs. 58, 59, pi. 7) the 

 multiple chromosome of the first spermatocyte metaphase is much 

 like that of Hesperotettix except in proportions. There is a 

 pronounced bend at one end at the point of fiber attachment, 

 but the other extremity is almost straight, only a slight sub- 

 terminal flexure indicating the place of the other fiber insertion. 

 In some instances this point is almost at the end of the chromo- 

 some. Individuals with this peculiarity are clearly distinguish- 

 able by somatic characters and, I believe, constitute a distinct 

 species. It is possible that, with fuller representation, forms 

 similar in the constitution of their multiple chromosomes to those 

 of Hesperotettix might appear. 



This type of hexad caused me much difficulty and led to the 

 conception of a decad chromosome. As will be noticed in fig- 

 ures 58 and 59, pi. 7, there are a number of constrictions along 

 the length of the chromosome quite constant in position, and so 

 placed as to indicate that there are five divisions or parts. It 

 will also be observed that the chromosome may be divided at 

 more than one of these levels. I can not now find any expla- 

 nation for these separations at various levels on the chromosome, 

 but that they are evidences of unions between various tetrads 

 is not indicated by the full history of the chromosome complex. 

 Again, in the anaphase and telophase of the first spermatocyte, 

 the composite nature of the larger V becomes marked. As may 

 be seen in figure 13 of a former paper ('05), one member of the 



