OV Til 10 OERM CELLS OF METAZOA. 



189 



the others. Probably two of the eighteen elements correspond to the two chromatin 

 nucleoli of the growth period, but I cannot determine which two they are ; if this is so, 

 then there would be here sixteen chromosomes (all apparently bivalent judging from their 

 dumbbell-shape on lateral view), and one bivalent and one univalent chromatin nucleolus. 

 But there can be no surety in regard to these valences without a knowledge of the num- 

 bers in the spermatogonia. 



31. Pwcilocapsus goniphorus Say 



Four testes of this species were studied. 



There were no spermatogonic mitoses on my preparations (all from adult individuals). 



In the rest stage of the spermatocytes there are present four bipartite chromatin 

 nucleoli (W. 2, Figs. 192-195, PL V), in one single case there were live (Fig. 191). The 

 largest of the four is composed generally of two rods placed side by side (this is shown 

 in lateral view in Figs. 191, 194, in end view in Figs. 192, 193, 195) ; the lateral view of 

 this one (the lower of the large ones of Fig. 191) sometimes shows that each of its com- 

 ponent rods may be transversely constricted, which might imply that each of the rods 

 is bivalent and hence that the whole is quadrivalent. In each of the three small 

 bipartite chromatin nucleoli the univalent components may be closely apposed to one an- 

 other (Figs. 191, 192), or may be more or less widely separated (Figs. 193-195). Of the 

 four chromatin nucleoli the largest and the smallest are generally attached to opposite 

 poles of the true nucleolus (N. '2, Figs. 191-194), though the relative positions vary con- 

 siderably as shown by the figures; and it is the two which are generally not so attached 

 which have their component parts most widely separated. 



Thus there are at least four, possibly five, bivalent chromatin nucleoli in the sperma- 

 tocytes. 



Pole views of the monaster stage of the first maturation mitosis show either seventeen 

 chromatin elements of approximately equal volume (Fig. 197), and this was the rule in 

 two of the testes examined ; while in a third testis in the majority of cases there was 

 present a smaller element in addition to the seventeen larger ones (/, Fig. 196); possibly 

 (his small element may always be present, but frequently escape observation by being 

 closely apposed to one of the larger elements. All these elements appear dumbbell-shaped 

 on lateral view (Fig. 198), and so are probably bivalent. 



How may of these eighteen elements axe chromosomes and how many are chromatin 

 nucleoli I cannot determine, since the number in the spermatogonia was not ascertained. 

 Possibly the small element (/ of Fig. 196) may represent the largest chromatin nucleolus 

 of the preceding growth period, and the seventeen remaining be chromosomes; or if all 

 four chromatin nucleoli are represented in the first maturation division, then there would 

 remain fourteen chromosomes. 



