360 



JOHN Mkl.LING. 



clearly visible; and it may be that there had been a horizontal 

 ring on the right, and a vertical ring on the left. 



FIG. 5. Two more selected metaphase to anaphase groups. The last two bivalents 

 in the lower line seem more or less malformed. 



BIVALENTS II AND III. 



Chromosomes II. and III. (Fig. i) doubtless differ slightly in 

 size, but are similar in behavior, and may be considered together. 

 They are long J chromosomes, with a large and a small segment 

 close together. At the late prophase (Fig. 2, Belling, 19256) 

 these two bivalents may have each the form of a large horizontal 

 ring with a small Y at one end, and a vertical portion consisting 

 of the two small segments at the other end. At the metaphase 

 (in Fig. 2, of the present paper), one of these bivalents forms a 

 ring with a small V, and the other a large and small ring in differ- 

 ent planes. Fig. 4 of the paper on the origin of mutations shows 

 bivalent II. forming a horizontal ring with a small vertical piece 

 consisting of the two small segments, and with a small loop 

 arising from the constrictions. In tin- upper line of Fig. 4 of the 

 present paper, this loop has increased in size in bivalent II. In 

 Fig. 4, lower line, and Fig. 5, upper line, bivalent II. shows part 

 of the small segments still in the equatorial plane, as well as a 

 ring (or ring and Y) on the other side. But in bivalents II. and 

 III. of Fig. 3, the small segments have been quite drawn into the 

 loop, and only the diminishing Y is left; or in bivalent III. of the 



