l'">8 MONTGOMERY A STUDY OF TJUO CHROMOSOMES 



the synapsis by the union into seven pairs of the fourteen chromosomes, each of the 

 seven bivalent chromosomes (pairs) being composed of two univalent chromosomes joined 

 end to end (Figs. 5-11). Where the ends of two univalent chromosomes come together 

 is seen a connecting band of linin ; each bivalent chromosome during the synapsis and 

 postsynapsis is U- or V-shaped, and the bend or angle of the U or V marks the point of 

 union of two univalent dhromosomes ; the arms of the U or V are longitudinally split. 

 In each bivalent chromosome only one end of each univalent chromosome is thus closely 

 connected with one end of the other, the opposite ends of the univalent chromosomes 

 having no such linin connections. It has been already mentioned that the two chromatin 

 nucleoli come together likewise to form one bivalent one, and it can be seen that they are 

 connected by a band of linin. 



In a paper on the spermatogenesis of Peripatm (1901) I showed that it is a particular 

 end of one univalent chromosome which .unites with a particular end of another; these 

 ends are the ones which point nearest to the pole of the spindle in the anaphase of the 

 last sperniatogonic mitosis, the " central ends," as I have called them, in distinction to the 

 opposite or " distal ends." In Euchistus, on the contrary, I am unable to determine 

 positively whether it is similar ends of chromosomes which unite, because in this form the 

 chromosomes have a much more irregular position within the nucleus ; the polarity of the 

 nucleus is not so well marked as in Peripatus. In the cell body the polarity is as in 

 Perlpatus: that pole with the greatest amount of cytoplasm and containing the idiozome 

 mass is the distal pole (the one which in the dyaster stage of the last spermatogonic 

 division was in the equator of the cell). This polarity of the cell body is shown in Figs. 

 4, 5 and 8 ; I figured it also in a number of cases in my previous paper, but then errone- 

 ously supposed the idiozome mass to occupy that point where the spindle pole had previ- 

 ously been, whereas I am now able to determine positively that this pole is situated 

 directly opposite, namely, where the least amount of cytoplasm is situated. Now it would 

 appear in Euchistus, though not nearly so regularly as in Perlpatus, that it is the openings 

 of the U- or V-shaped bivalent chromosomes that are directed toward the distal pole of 

 the cell body (toward the pole where the idiozome mass is placed). Figs. 4, 5 and 8 

 show this for certain of the chromosomes, while other ones (as two in Fig. 5) may have 

 their openings in opposite directions. Thus in Euchistus there is more irregularity in the 

 positions of ^ the axes of the chromosomes, so that I have been unable to determine 

 whether it is, as in Peripatus, only particular ends of the univalent chromosomes which 

 unite with particular ends of others. 



Throughout the growth period can be seen two kinds of liuin threads : (1) thicker 

 threads which connect the ends of the chromosomes, and (2) more delicate ones which 

 join chromatin granules with the nuclear membrane. Apparently, as I have shown for 



