GERM CELLS IN PEDICELLINA AMERICANA 23 



Heidenhain's h?ematoxylin it can be made to stain intensely, so 

 that at times it becomes impossible to distinguish the chromo- 

 somes with which it is connected. On continuous extraction, 

 however, this difficulty can be readily overcome, and finally 

 nothing but the deep staining granular chromosomes remain in 

 view, with but the slightest trace of the linin, — sufficient only 

 to show the true relation existing between the former and the 

 latter. 



Up to this point the development of the egg and the sperma- 

 tozoon has followed, very closely, along the same lines. In 

 the several generations and nature of the oogonia and sperma- 

 togonia ; in the presence of the V's in the last oogonial and 

 spermatogonial telophase, with its consequent reduction of the 

 chromosomal number ; in the further history of the bivalent V's 

 thus formed ; their lengthening, their irregular distribution 

 within the nucleus, and finally in the longitudinal splitting of 

 their arms, the early male and female germ cells are quite 

 alike. It is now necessary to trace those processes which from 

 this point onward, transform the longitudinally split bivalents 

 into the characteristic figures of the first maturation-division, 

 and to compare them with the corresponding changes in the 

 sperm. 



The chromosomes, now longitudilly split along their entire 

 length, begin to show very characteristic changes. As in the 

 sperm, the acute angle of the V's gradually opens out, until, at 

 a later period of development, it becomes equal to i8o° and the 

 chromosomes become nearly straight longitudinally split bodies 

 (Figs. 78-79). In this movement the arms swing each around 

 the apex of the V (the point of synapsis). This process does 

 not occur at any fixed time, nor do all the chromosomes act 

 together in this regard. In the end, however, the changes in 

 all are quite alike. The chromosomes move toward the per- 

 iphery of the nucleus. Fig. 79, where they lie below the nuclear 

 membrane, in the form of almost straight longitudinally split 

 threads. We are here again reminded of the observations in the 

 eggs of the Copepods, where Riickert, '94, and Hacker, '92 and 

 '95, found the same conditions of the chromosomes (cf. Figs. 



