468 E. ELEANOR CAROTHERS 



Stenobothrus. This latter genus has but nine chromosomes in 

 the reduced series (seventeen in spermatogonia) . Three of these, 

 however, are rings which present a typically different appear- 

 ance from the remaining five tetrads. The basis of this dif- 

 ference is that they have entered the spindle extended parallel to 

 its axis and have nonterminal fiber attachment. Robertson 

 holds that these three chromosomes are really multiples; their 

 point of union being represented by the position of the spindle 

 fiber attachment. This would give twelve (the number typical 

 for the Acrididae) as the real number of chromosomes in the 

 haploid series. Woolsey ('15) has clearly shown such a linkage 

 of chromosomes to be correlated with a reduction in number in 

 several species of a Locustid genus. Furthermore, McClung ('16) 

 has found conditions similar to those discribed by Miss Woolsey 

 among the individuals of a single species of Hesperotettix. 



The difficulty is, that Robertson puts forward a hypothesis 

 that nearly all rings of the Stenobothrus type are multiples and 

 are correlated with a reduction in the number of chromosomes. 

 This is clearly not the case as regards either Trimerotropis (forms 

 A and B) or Circotettix, for both have numerous tetrads of the 

 Stenobothrus type and Trimerotropis has the normal number of 

 chromosomes (twelve) while Circotettix has but one less. The 

 number of rings of the Stenobothrus type varies from individual 

 to individual, but the number of chromosomes is constant. In 

 addition, the transition stage (J-shaped tetrad) between chromo- 

 somes of the Stenobothrus type and those of the Hippiscus type 

 is present in these species. A further argument against the 

 above hypothesis is the secondary shifting of the point of fiber 

 attachment on certain chromosomes (figs. 22c and 22d, plate 14). 



It is clear that we have two fundamentally different types of 

 rings which are so similar morphologically that unless we get 

 transition stages, as Woolsey ('15) has in Jamaicana and McClung 

 ('16) in Hesperotettix, we have no criterion by which to separate 

 them. Both enter the metaphase extended parallel with the 

 axis of the spindle, both have non-terminal spindle fiber attach- 

 ment, both give double V's in anaphase and both may occur 

 where there is reduction in number without all of them being 



