SYNAPSIS .\ND CHROMOSOME ORG.-ySTIZATION 505 



Robertson ('16) is persuaded that all the autosome pairs 

 divide reductionally in the first division. He bases this conclu- 

 sion on the interlocking tetrads which he found in Chorthippus, 

 the beha\dor of the 'bi-tetrads' in Jamaicana (Woolsey, '15), 

 the segregation of unequal rods in the first division described 

 by Hartman ('13), Carothers ('13), and Robertson ('15), and the 

 pre-reductional division of the multiples in Hesperotettix and 

 Mermiria (McClung, '05). 



He says (p. 246) : "From the instances which I have here given 

 it seems to me the inference may possibly be drawn that all 

 autosomal tetrads will be found to divide reductionally in the 

 first maturation division." 



In Phrynotettix I found one unequal pair which apparently 

 always divided equationally iii the first division and another 

 which did so half the time. I was also able to show that Chromo- 

 some A in Phrynotettix, though the conjugants were of equal 

 length, nevertheless divided equationally in the first division, 

 and I believe that a similar behavior is clear for chromosome 2 

 in Trimerotropis. With these different facts established, the 

 variability of behavior in the telomitic chromosomes \\T.th regard 

 to reduction must be recognized, and, further, in the case of the 

 atelomitic chromosomes it seems unwise to attempt to estabhsh 

 a general rule. 



C. Chromosome organization 



a. Atelomitic, or V-shaped chromosojyies. The idea of multiple 

 or compound chromosomes was first presented for Orthopteran 

 material by McClung ('05). In a paper in this journal Dr. 

 McClung considers this subject in a comprehensive manner so 

 that it will be unnecessary to discuss here more than a comparison 

 between the chromosomes of Chorthippus and Trimerotropis. 



The occurrence of a constriction or transverse cleft at the 

 apices of the atelomitic chromosomes has been noted several 

 times and I have already mentioned the view that Robertson 

 ('16) has taken in regard to the possibly compound nature of the 

 atelomitic chromosomes of Chorthippus. In drawing his conclu- 

 sion that these chromosomes are compound, Robertson makes 



