SEGREGATION OF HOMOLOGOUS CHROMOSOMES 449 



2. Nomenclature 



The unusual conditions of the chromosomes in this group 

 have made advisable the introduction of four new terms. 



1. Homomorphic — used to designate those tetrads made up 

 of morphologically similar homologues. 



2. Heteromorphic — used to designate those tetrads made up 

 of morphologically different homologues. 



3. Telomitic — a term used to indicate terminal fiber attach- 

 ment. 



4. Atelomitic — a term used to indicate nonterminal fiber 

 attachment. 



The two latter are extensions of the ideas involved in the 

 terms 'Hippiscus type' and \Stenobothrus type' as used by 

 McClung ('14). This has seemed desirable since the work of 

 Robertson ('16) and some recent work of McClung indicates 

 that the chromosomes of Stenobothrus may be fundamentally 

 different from those of the typical Acrididian complex. I shall 

 also apply the terms telomitic and atelomitic to spermatogonial 

 and somatic chromosomes as well as to those of the first sperma- 

 tocyte. The term Hippiscus type will be used interchangeably 

 with telomitic for those first spermatocyte chromosomes which 

 are comparable in structure to the Hippiscus rings. However, 

 in this material the tetrads of the Hippiscus type are usually 

 transformed into rods in the metapha-e as described by Mc- 

 Clung ('14). In the same way Stenobothrus type and atelo- 

 mitic may be used interchangeably. 



3. Special fitness of material 



The genus Trimerotropis is confined to the American conti- 

 nent and contains over thirty species, the extreme members of 

 which merge with those of four other genera. The present 

 paper deals with the fallax group of the genus and its relation 

 to the genus Circotettix, with especial reference to the hetero- 

 morphic tetrads found in each. In regard to the systematic 

 relationships, it is believed that a definite cytological criterion — 



