CHROMOSOME STUDIES 231 



parallel arrangement of the leptotene threads, the side-to-side 

 pairing of homologous chromosomes begins at the free ends of 

 the members of each pair; i.e., the ends which lie at the dis- 

 tal pole of the cell, and advances along the pair toward the 

 opposite ends. In the case of V's, pairing should begin at the 

 distal ends of their limbs, and move toward the apices (Schreiners, 

 '06a, figs. 20-26). The distal ends of the chromosomes lie in 

 the distal part of the cell; i.e., that part which contains the 

 interzonal body and is nearest to the plane of the last division 

 (Davis, '08, p. 81). There would then result from V-pairs — of 

 which according to Muckermann ('13) there are in urodeles 

 about seven or eight — the familiar loops of the 'bouquet stage,' 

 characteristic of so many species. 



In those species where no V's, but only straight rods, occur 

 the loops, such as Janssens ('05, fig. 42) and the Schreiners 

 ('06a, figs. 20f, 20h, 22, 25, 26) have shown in this stage, would 

 not appear. I have found this to be true in the Tettigidae (my 

 unpublished "Study 11"), where this stage, from its resemblance 

 to a sheaf of wheat, might appropriately be termed the 'sheaf 

 stage. Wilson ('12, p. 387) has not been, able to find the 'bou- 

 quet-stage,' nor the polarization that goes with it, in any of the 

 Hemiptera. Here the chromosomes are short, which may ac- 

 count for the lack of polarization. Davis ('08, figs. 31-34) 

 describes for Dissosteira (a rod-chromosome genus) what he 

 took to be the loops in the 'bouquet-stage;' but I think he has 

 wrongly interpreted as 'loops' what I believe are the much 

 bent, long rod-chromosomes ('10s and ll's of Syrbula) inti- 

 mately paired side-to-side. The extreme length of the paired 

 thread in such cases has caused it to bend and simulate the 

 loops of Tomopteris or Batrachoseps. But if one look carefully 

 at Davis's figures, it will be noticed that only one limb of each 

 'loop' lies completely within the region of the distal pole of 

 nucleus and cell. The other end may, in some cases (the longer 

 chromosomes), lie not far from this pole, but more usually it 

 is in the region of the opposite (proximal) pole, or on the right 

 or left side of the nucleus. Many investigators (Montgomery 

 '05, Davis '08, and others) have made this mistake in attempt- 



