212 WM. REES B. ROBERTSON 



Clung's chromosome in Hesperotettix and Mermiria, which 

 likewise was associated with the sex chromosome, but more 

 permanently than in Chorthippus. 



The long chromosome (7-11) in figure 165 is clearly split 

 into two strands and optical cross-sections at favorable points 

 (a and b) show that each of the halves is again split. In the 

 middle at the points x, x, the halves gape apart. These points 

 correspond to what would be the proximal points of chromo- 

 somes 7 and 11, were they going through this pairing process 

 separately, as they do in Syrbula (fig. 149). 



In figures 166, 167 a and 167 b are chromosomes in the same 

 stage as figure 164, which show clearly the four longitudinal 

 parts. The black points at the ends are probably the polar 

 granules. In figure 168 is a still later stage where the chromo- 

 somes are more condensed, but still show their two longitudinal 

 splits and the resulting four strands. At any point along the 

 chromosomes the strands are usually more closely apposed in 

 one direction than in the other, according as the primary or the 

 secondary split is farther advanced. The letters "x, x" mark 

 the points where the attraction fibers were destined to spring 

 forth, for at these points there is a constriction in the long chromo- 

 somes (7-11, 8-10, 5-9). In figure 164 nos. 10.T and 4 have been 

 drawn outside the nucleus for convenience. Figure 173 is of a 

 still later stage. Chromosomes nos. 3, 6, and 7-11 (173a) have 

 been drawn outside the nucleus (173b) for clearness. The sex 

 chromosome, as usual, lies near no. 4. 



In the next older stage (fig. 174) the chromosomes have be- 

 come more condensed. No. 4 takes on its usual shape, a modi- 

 fied cross. Nos. 1, 2, and 3 are rods, which have already opened 

 out by rotation so that the primary split is represented solely 

 by the region of contact where the distal ends of the halves 

 resulting from this split still meet. The compound nature of 

 nos. 7-11 is evident. The proximal points (x, x) are marked 

 by constrictions. The smaller of the two chromosomes, no. 7, 

 forms an almost complete ring in the plane of the drawing paper. 

 The larger (no. 11) part forms a ring similar to that of figure 156d. 

 The ring perpendicular to the plane of the paper is the link in 



