I ; JAMES O. FOLEY. 



of Y's arc to be seen. These may have been produced either by 

 the cutting across of some of the previously described loops, 

 or they may be due to a further contraction of the loops in which 

 the bivalents at one end of the V have entirely united while the 

 other end still shows the split which may be observed in the 

 various diakenetic figures previously cited. The double split 

 indicating the tetrad nature of these chromosomes, is not evident 

 until they come upon the metaphase spindle of the first matu- 

 ration division where end views can be secured (Fig. 36). At 

 this stage, however, the tetravalent nature of the chromosomes is 

 readily observable after proper staining and destaining methods. 

 No irregular behavior, such as lagging or irregular divisions 

 (Fig. 37) in early or late anaphase, was seen in these chromo- 

 somes. They pull apart forming dyads (Figs. 39 to 41), eleven 

 in number in each daughter cell or secondary spermatocyte. 



THE SECOND MATURATION DIVISION*. 



The secondary spermatocytes (Fig. 38) are about one-third 

 smaller than the spermatogonia which entered the first matu- 

 ration division. Although resting nuclei (Fig. 38) are formed not 

 infrequently, in secondary spermatocytes, the more common 

 method of procedure is for the telophase of the primary spermato- 

 cyte to become rearranged immediately into the metaphase of the 

 secondary spermatocyte. Both Geiser ('24) working on Gam- 

 bit sia, and Agar ('u) on Lepidosiren found likewise that no 

 resting stage occurs between the telophase of the primary and 

 the metaphase of the secondary spermatocyte. The writer 

 believes that the condition found depends mainly upon the 

 rapidity with which cell-division is going on. When tin- rate is 

 slow a resting stage will be found but when rapid it is dispensed 

 with. In Umbra the transition period brt \vivn primary and 

 secondary spermatocytes as well as the time of the secondary 

 spermatocyte division itself is usually very brief. Figs. 39 to 41 

 show such a rearranged metaphase in which the chromosomes 

 retain their definite bivalent condition. They still show their 

 dyad nature plainly when at ihe equator (Figs. 39 to 41) of the 

 spindle for the metaphase of this division. At a somewhat later 

 time (Figs. 42 and 43) they tend to fuse or adhere to one another 



