CHROMOSOME STUDIES 237 



authors have so interpreted, and since we may be reasonably 

 certain that in the case of the compound chromosomes of 

 Chorthippus such has occurred. The fact that gaping-apart 

 occurs between the two strands at the middle of the compound 

 chromosomes, and that a similar phenomenon occurs in Tomo- 

 pteris and Batrachoseps, where the Schreiners have shown that 

 parasynapsis takes place first at the free ends of the limbs of 

 the V's, forces one to believe that in Chorthippus likewise we 

 may expect to have parasynapsis beginning at the free ends of 

 each pair of V's. It seems perfectly possible, then, that in this 

 process of simultaneous approximation of the distal ends of each 

 pair of limbs of a V pair there may be accidental interlocking 

 between the members of two pairs of V's, such as we find in 

 figure 163, between the 8-1 0's and 7-1 1's, or, as appears to have 

 been the case in the pairs shown in a later stage at figure 177, 

 or, still better, the interlocking which the Schreiners ('06b, figs. 

 24, 25) have described in Salamandra. It seems to me that 

 such figures can be explained only on the assumption that the 

 phenomena have taken place in the manner I have set forth. 

 If we admit that the interlockings just described have resulted 

 during approximation side-to-side of pairing V's, then the pres- 

 ence of such conditions in the stage when separation (fig. 163) 

 is evidently beginning, means that the split appearing at the 

 middle of chromosomes 7-11, 8-10, 5-9, must be the split of 

 reduction, and that this stage must mark the beginning of the 

 separation of homologous chromosomes. For, following this 

 split through figures showing these compound chromosomes, 

 it is evident that it gives rise to the space of the middle or per- 

 pendicular-ring portion of each compound. This middle ring 

 may, as before said, be thought of as being formed by the four 

 proximal knob-like parts of the two pairs, 7's and ll's, 8's and 

 lO's, etc., which have become linked to form the compound 

 (compare figs. 155-158 with 174-180). The points of con- 

 striction, from which the attraction fibers spring at the opposite 

 sides of this ring, are evidence of this. The terminal portions 

 of the compound — ^forming horizontal rings, if the rod chromo- 

 somes involved be long (ll's, lO's, or 9's), or horseshoes, crosses, 



