GENETICS OF HETEROMORPHIC CHROMOSOMES 461 



III. OBSERVATIONS 



The principal object of this paper is not to trace the spermato- 

 genesis of Cii'cotettix verruculatus, but to show as graphically 

 as possible the genetic relationship of the chromosomes of the 

 male and female involved in particular matings to those of their 

 offspring. The plates accordingly are made up with the first 

 spermatocyte chromosomes used as the standard, the sperma- 

 togonial complex and the somatic complexes of the females being 

 rearranged so that supposedly homologous chromosomes^ fall in 

 vertical rows. A general knowledge, however, of the range of 

 chromosomal conditions which, from the frequency of their 

 occurrence in wild individuals, may be considered normal for 

 the species is essential to a proper study of the specific matings. 

 The following description based on a study of sixty-eight wild 

 individuals is typical for members of the species from two local- 

 ities, Manchester, New Hampshire, and Pigeon Cove, Massa- 

 chusetts. 



1. Description of general chromosomal conditions in the species 



a. Tijpical conditions. C. verruculatus, like all of the species 

 of the genus so far studied (unless Trimerotropis suffusa Scudd. 

 be considered a Circottettix) , has normally twenty-one chromo- 

 somes in the spermatogonia instead of twenty-three, the basic 

 number in the short-horned grasshoppers. The spermatogonial 

 complex (pi. 1, row 2) has constantly nine large atelomitic 

 chromosomes (those with non-terminal fiber attachment) (nos. 6, 

 9, 10, 11, 12) and six telomitics (those with terminal fiber attach- 

 ment) (nos. 2, 4, 5). The remaining six (nos. 1, 7, 8) may be 

 individually of either type, but any given form is constant for a 

 particular specimen. The diploid complex of the female is 

 similar except for the presence of one additional accessory, giving 

 constantly at least ten large atelomitics (pi. 1, row 3, nos. 6, 9, 



3 Size, morphology, and comparison with the component members of the 

 tetrads have been the criteria used for determining homologues in the diploid 

 complexes. In regard to the critical pairs numbers 1, 7 and 8, there can be no 

 reasonable doubt since they are easily identified. For most of the other pairs 

 the arrangement is only approximately correct both as regards the selection of 

 homologues and the arrangement in the size series. 



