278 CALKINS. [Vol. XI. 



contains thirty-two chromosomes (Fig. 9). The nuclei enlarge 

 after this final division and the entire spermatosphere increases 

 in size (compare Figs. 4, 6, and 12). The archoplasm also is 

 large and distinct (Fig. 4, A). 



The resting nuclei of this stage are large and round and 

 exhibit well marked nucleoli. It has been frequently stated 

 that, in the case of developing spermatic cells, the nucleolus is 

 thrown into the cytoplasm ; this certainly does occur in Lu7n- 

 briciis (Figs. 44 and 46), but from the nature of these prepara- 

 tions (these results were seen in only one series of sections) I 

 have not the least hesitancy in asserting that the phenomenon 

 is here an artefact. 



After a period of rest (Fig. 10) during which the cytoplasmic 

 cleavages deepen, the nuclei begin their period of greatest 

 activity. The chromatin collects at one portion of the nucleus 

 in a rather small lump (Fig. 11) which afterwards expands and 

 becomes mesh-like, while fine offshoots of chromatin soon 

 appear (Fig. 12), The chromatin elements grow during this 

 period and a thick spirem is formed, nearly filling the nuclear 

 space. The thread is ragged at first (Fig, 12), but later 

 becomes apparently smooth (Figs. 12 and 13), In favorable 

 preparations the spirem is seen to be split longitudinally, and 

 is therefore double (Fig, 12, D). The cell elements are much 

 too small and the spirem much too twisted and interlooped 

 to tell whether it is one long piece. In one case, however 

 (Fig, 13), I was able to see that at most there were only two 

 pieces. Later the spirem becomes transversely segmented into 

 many rod-like bodies (Figs. 14 and 15), which at first appear to 

 be without order, but in later stages are found to be definite 

 both in number and in structure. It is then seen that there 

 are thirty-two of these bodies and that each is double (Fig. 16), 

 From them the " Vic7'ergnippen " are formed by a process differ- 

 ing widely from the method usually described. The thirty-two 

 double chromosomes unite two by two (Figs, 17-20), and are 

 finally arranged in sixteen quadruple groups (Fig. 21). In some 

 cells four quadrivalent groups were seen, together with twenty- 

 four double chromosomes ; in others twelve quadrivalent groups 

 and eight double forms were seen (Fig. 19). 



