564 . CLARENCE E. McCLUNG 



has been found in complexes of less than the full twenty-three 

 numbers, some uncertainty existed regarding the connection 

 between these two circumstances. That this connection was not 

 necessarily causal was indicated by the case of the unidentified 

 ' Stenobothrus-like' species with a complex of twenty-one and 

 numerous rings of this species-type. But not until the work of 

 Carothers on Trimerotropsis was it certain that there is no 

 necessary relation between the Stenobothrus ring and lesser 

 chromosome numbers. It is now clear that this form of chro- 

 mosome is not in itself evidence of multiple constitution above 

 the tetrad. Structurally all that is involved, apparently, is an 

 atelomitic fiber attachment. 



But if it is not true that such rings and the double-V's which 

 unite to form them, and which reappear upon their division, are 

 criteria for octads, it is very suggestive of such composition to 

 find them so frequently in cases of reduced numbers. Where it 

 can be shown that progressive steps in such unions occur within 

 a species, as in H. viridis, and that morphologically recognizable 

 divisions of these elements which, if counted as units, exactly 

 restore the reduced number to that characteristic of the species 

 and family, then the form of the chromosome is of value in 

 determining composition. Especially is this true if by such means 

 always the exact number characteristic of the group is restored, 

 and if, in groups of different chromosome numbers, the distinc- 

 tive numerical relations are preserved. All of these desiderata 

 are realized in Hesperotettix of the twenty-three chromosome 

 family and in Jamaicana of the thirty-three and thirty-five group 

 as reported by Woolsey. The parallel between the two cases 

 seems to be very exact, with the exception of a more marked 

 tendency toward combinations in Hesperotettix. 



The circumstances appear unequivocal in the cases of Hespero- 

 tettix and Jamaicana where multiples may or may not exist within 

 one species and where intermediate steps indicate the method of 

 combination. The question which next presents itself is with 

 regard to the application of these criteria to cases, such as Chor- 

 thippus, where there appears to be a permanent and fixed re- 

 duction of number, not only for the species, but also for the 



