234 WM. REES B. ROBERTSON 



163) only two pairs of these knobs appeared; in the four-strand, 

 four pairs. Between the two thickenings on each strand (figs. 163, 

 174, 176, 178) is a constriction and segmentation which is identi- 

 cal with the non-staining region at the apex of the V-chromo- 

 somes of the spermatogonia (fig. 162) and is similar to that which 

 occurs in the V's of Lepidosiren and Trillium and the bipartite 

 rods of Copepoda. This constriction divides each of the three 

 four-strand spiremes into two unequal parts, corresponding in 

 length with the limbs of the three respective pairs of spermato- 

 gonial V's. The facts, (1) that the position of these knobs 

 and the constriction of the filament between them corresponds 

 with that of the constriction and apices of the three pairs of 

 V's. respectively, and (2) that there is among the three long 

 spiremes but one such t*?? equally segmented spireme for every 

 pair of V's, and further (3) that such single segmented spireme 

 cannot have resulted from a pair of V's in telosynapsis (since 

 the segments of each of the three long spiremes are unequal) 

 and (4) that the presence of all other spiremes in these nuclei 

 has been accounted for, lead to the conclusion that in these 

 three long spiremes of Chorthippus we probably have the re- 

 sult of a parasynapsis of each of the three pairs of V-chromo- 

 somes, which took place at some previous time. The ends of 

 the spiremes represent the distal ends of the limbs of the V's 

 and their knobs the proximal or apical region of these V's. If 

 this be granted, then the autosome spiremes in Syrbula corre- 

 sponding to the limbs of these V's must also be in parasynapsis, 

 for in each case their behavior is similar *to that of the V's. 

 Since the remaining five autosomes in Syrbula and Chorthippus 

 are similar to these three — each of them splitting into four longi- 

 tudinal parts — I believe that all autosome spiremes, eleven in 

 Syrbula and eight in Chorthippus, have united at some previous 

 time in parasynapsis. 



The remaining figures of the first maturation chromosomes of 

 Syrbula and Chorthippus I shall, for convenience, group into 

 four stages, H,^ 'j,' 7^,' and 'I,' but will discuss them together. 

 Stage 'i,' early to middle prophase, includes figures 150, 152, 

 153 of Syrbula and figures 174 to 177 of Chorthippus; stage 'j,' 



