CHROMOSOME STUDIES 257 



bers of such a pair, but apparently no irregularities do occur. 

 The V travels to one pole and its rod-mates to the opposite pole. 

 They separate in the form they had on entering the pairing proc- 

 ess. However, this is not contending that there is no possibil- 

 ity of a break at the apex of the V member of this bi-tetrad and 

 a relinkage of one limb of the V with one of the free rods or with 

 a limb of an opposite V. If such occurred, it would, of course, 

 be a 'crossing over' carrying a large group of factors. 



I wish to call attention to some of the peculiar mitosis figures 

 which Janssens gives in support of his theory. The gaping 

 apart of the distal ends of halves of exconjugants, which be be- 

 lieves to be abnormal (text fig. XXIII, XXIV and figs. 40, 

 41a, 41b, 47, 48, 50-52), is in reality not unusual for chromosomes 

 of the Tettigidae and Acrididae. The twistings shown in ana- 

 phases, such as his figures 17, 18, 24, 30, 31, may be explained 

 as the result of misfortune in the prophase. Frequently I find 

 such a chromosome as figure 17 in various prophase periods from 

 late H^ up to the metaphase in the same condition, the only 

 difference being in the degree of condensation. In stages ^K 

 and 'i,' when such a chromosome is in the long-spireme condition, 

 split into four strands and coming out of disjunction, it is to be 

 expected that the four strands composing it will get twisted into 

 all sorts of positions before turgidity (rigidity) sets in as a result 

 of the condensation process. That, however, it seems to me is 

 no argument for the breaking and re-fusing of any two of these 

 filaments. I have similar chromosomes in no. 11 of figure 155b 

 and 7-11 in figure 175. 



But my chromosomes 5-9 in figure 178 cannot be explained 

 as the result of a twisting in the disjunction process. Janssens 

 has shown in his figure 14 a chromosome of the same nature. 

 His chiasma-type theory, it seems to me, fails to explain the 

 persistence of such twistings. It seems to me that this might 

 be explained more readily if the splitting of the conjugating chrom- 

 osomes and a twisting were to occur' in each conjugant before 

 sider-to-side pairing takes place. Such might be expected in 

 compound chromosomes of the V type in which pairing possibly 

 begins simultaneously at the distal ends of both limbs of the 



