GERM CELLS IN PEDICELLINa AMERICANA 11 



the last division. The chromosomes now come closer together 

 along the converging spindle-fibers (Figs. 14-16) and finally, 

 in the early telophase (Figs. 17-18), appear at each pole, in the 

 form of about eleven (the reduced number) of Vs. Owing to 

 the increased size of the individual chromosomes, and the cor- 

 responding halving of their number, the concentration in the 

 telophase into one impenetrable mass, so characteristic of the 

 earlier generations of spermatogonia, is not so marked. As the 

 several figures show, the chromosomes are, in most cases, indi- 

 vidually distinguishable, and (as in both cells of Fig. 18) can 

 readily be studied. The evidence therefore, unmistakably indi- 

 cates that the eleven V's have arisen from the twenty-two rod- 

 shaped bodies, which have united end to end during the latter 

 part of the process of division ; and that, as in Peripatiis and 

 the other forms studied by Montgomery, the reduction takes 

 place at this point. The true " synapsis " is therefore not to be 

 sought in some stage in the early growth period of the sper- 

 matocyte, but in the latter half of the last spermatogonial 

 division, as Montgomery and Sutton have insisted. 



After the process of synapsis, the nuclear membrane reforms 

 and the spermatogonia are now spermatocytes (Fig. 19). These 

 are readily distinguished by a marked polarity, such as has 

 been described by most workers on spermatogenesis. The 

 nucleus, now takes up nearly the whole content of the cell and 

 the chromosomes, localized at one end of the nucleus, have re- 

 tained the same form in which they appeared in the preceding 

 telophase, i. e., as V's. A growth period now sets in w^hich, 

 judging from the great numbers of cells found in this stage and 

 from the complicated processes through which the chromatin 

 passes, must be one of considerable duration. The arm of the 

 V's have already much increased in length, and are no longer 

 congested at one pole, the majority extending across the whole 

 breadth of the nucleus. The apices now touch the membrane 

 at many points (Fig. 20). It is interesting to observe also, that 

 the rate of growth in the several chromosomes varies consider- 

 ably. Thus Fig. 20 shows three bivalents of full size, while the 

 remaining ones are very little larger than at the beginning of 



