450 E. ELEANOR CAROTHERS 



difference in number of chromosomes — has been found for sepa- 

 rating the two genera. 



On this evidence the species suffusus belongs to the genus 

 Trimerotropis instead of to Circotettix, while the heteromorphic 

 tetrads found in both genera may point to a common origin. 

 Furthermore, the evidence, as will be shown, indicates that the 

 fallax group constitutes a single species. 



The group which forms the basis of this work is known to 

 taxonomists as one of the most difficult to classify. Certain 

 species of the group have been removed to the genus Circotettix 

 by some taxonomists, while others have split up the remainder 

 into four species. If one assume that the chromosomes are 

 direct descendants from ancestors morphologically like them- 

 selves, are the bearers of the determiners of the hereditary 

 characters, and that the homologues actually express, in their 

 architecture, differences in the determiners, the results of a study 

 of the maturation divisions in the male leave little surprise that 

 taxonomists are bewildered. 



Dr. McClung has shown ('14) that the point of spindle fiber 

 attachment is normally constant, but at some period in the his- 

 tory of this species there must have been a reorganization to the 

 extent of a shifting of the attachment in certain chromosomes. 

 The most striking result has been to produce J-shaped tetrads 

 in the first spermatocyte. Such shapes are due to one homo- 

 logue being rod-shaped; that- is, it has terminal fiber attachment, 

 while its mate has nonterminal fiber attachment. Of the 

 twelve first spermatocyte chromosomes, ten tetrads and the 

 accessory are affected by this reorganization. If the female is 

 similarly involved and if there is free fertilization, bringing about 

 chance recombination, one might expect to find in a given indi- 

 vidual all ten of the tetrads represented by two rod-shaped homo- 

 logues, giving rod-shaped tetrads, or one might find all of the 

 homologues with nonterminal fiber attachment, resulting in 

 tetrads of the Stenobothrus type (McClung '14). Between these 

 two extremes there might be present every possible combination 

 in J's, rod's and Stenobothrus-like rings. 



