252 WM. REES B. ROBERTSON 



the V's of Chorthippus and Jamaicana, in which no pairs have 

 arms of equal length. These conditions make it improbable 

 that the V is a pair of homologous chromosomes in telosynapsis. 

 It is self-evident, that neither the separation from each other of 

 unequal homologous chromosomes in Tettigidae nor the separa- 

 tion of the V from its rod-chromosome mates in Jamaicana. sub- 

 guttata during the first maturation division, can be explained 

 according to Haecker's metasyndesis theory. 



In regard to the complete fusion of homologous chromosomes 

 during parasynapsis, as held by Bonnevie and Vejdovsky, I 

 have again some very important evidence in the unequal homol- 

 ogous chromosomes, and likewise in the V's of Jamaicana and 

 Chorthippus. I have discussed in full with figures (Robertson 

 '15, plate 3) in my Studies III the evidence afforded by the 

 unequal pairs. In Chorthippus the interlockings which I have 

 found between the no. 8-10 and 7-11 compounds (fig. 163) 

 and between the 5-9 and 7-11 compounds during the middle 

 and late synapsis periods, together with two cases that have been 

 illustrated by the Schreiners ('06b, figs. 24, 25), furnish strong, 

 though rare, evidence that these pairing chromosomes during 

 the parasynapsis period have maintained their individuality 

 as chromatin threads. I am convinced by my work upon the 

 Tettigidae (Study II) that parasynapsis is a fact in grasshoppers. 

 The three long asymetrically segmented spiremes in Chorthip- 

 pus, as I have already explained, furnish indirect evidence that 

 parasynapsis must have taken place. If we accept the evidence 

 of the Schreiners and of Janssens, side-to-side pairing probably 

 begins at the distal ends of the limbs of a V pair. This takes 

 place, according to them, previous to, or about the time of, the 

 bouquet period and soon after the last spermatogonial division. 

 It is apparently possible that the interlockings between V pairs 

 which I have described might have occurred at this time. Fol- 

 lowing this period of side-to-side approximation, is a period of 

 intimate side-to-side pairing, which passes into a period, the ^g' 

 stage of Wilson, in which individual spiremes cannot be made 

 out. Yet we find the spiremes coming out of this period in the 

 reduced number and in the same relative sizes as are the auto- 



