490 E. ELEANOR CAROTHERS 



in one of the three pairs of euchromosomes, the presumption 

 is that these two genes, rather than either of the two large 

 groups of non-sex linked genes, lie in the microchromosomes. 

 Should such prove to be the case, these would be the first in- 

 stances of definite somatic characters being associated with a 

 definite, recognizable euchromosome. 



Dr. McClung, in two papers ('05 and '08), pointed out the 

 general possibilities of cytological work and stated clearly his 

 ultimate aim (p. 326, '05), "To determine the relation between 

 individual chromosomes and- characters in the body." For such 

 a purpose the advantages of a species like Trimerotropis fallax 

 or Circotettix lobatus is obvious. Taxonomically, there is 

 striking individual variation, and correlated with this, apparently, 

 are definite morphological variations, already described, of the 

 homologous maternal and paternal chromosomes. Here, then, 

 we have in a single species the means of distinguishing between 

 certain homologous chromosomes. There is the further ad- 

 vantage of freedom from the sterility and lack of viability (if 

 one may judge by the plentifulness of the animals) usually 

 associated with hybrids. Of course it follows, that any ratios 

 obtained through genetic work on these forms should be accurate, 

 whereas those based on hybrids where there is a high degree of 

 mortality, cannot be reliable. 



So far no attempt has been made to breed these species, all 

 of which, unfortunately for a worker located in the east, are 

 Rocky Mountain forms. Another species of Circotettix occurs 

 in mountainous regions of the east and, should it be as favor- 

 able cytological material as the western forms, I hope to do 

 breeding work with it. 



It might be said in passing that, according to my experience 

 with several local species, grasshoppers are proving very favor- 

 able subjects for breeding. They stand captivity well and can 

 accommodate themselves to various food and temperature 

 conditions. They show strongly marked characters, breed 

 freely, and it is possible to obtain three or four generations a year, 

 at least of some species, by keeping them constantly at about 

 39°C. Special laboratory facilities, while convenient, are by no 

 means essential since the eggs of most species normally live 



