BIGELOW : NUCLEAR CYCLE OF GONIONEMUS MUEBACIIII. 373 



has been demonstrated in Scolopendra by Blackmail (: 05), aiid in an 

 even more conviucing manner in insects by Sutton (: 02) and Baumgart- 

 ner (:04). In animals, on the other hand, in which the chromatin is entirely 

 diffused during the resting stage of the primary spermatocyte, — e. y., 

 worms and coelenterates, — early synapsis has never been discovered, 

 while in some of them, such as Ascaris and Gouionemus, it is doubtful 

 whether any actual synapsis of individual chromosomes takes place at 

 all. I realize, however, that the evidence on this point is by no means 

 conclusive ; it is only by a renewed examination of molluscs, worms, 

 echmoderms, and coelenterates that a sound decision can be reached. 



c. The Pseudoprophase of the Oocyte. 



The occurrence of an abortive attempt at mitosis in the development 

 of the female germ cell, although unusual, is not unparalleled. Selenka 

 ('81) described a similar process in Thysanozoon, in which the nucleus 

 of the young oocyte undergoes the ordinary series of prophase changes, 

 proceeding as far as the formation of the achromatic spindle. But after 

 the metaphase regression follows, with the result that the nucleus re- 

 turns to the " resting " condition without dividing. Selenka has shown 

 beyond doubt that he was not examining any part of the first matura- 

 tion division, for he remarks that while the abortive prophase takes place 

 in the ovary, the maturation division does not occur until after the egg 

 is laid. More recent students of the same animal — van der Stricht 

 ('96'), Schockaert (: 01) — have found no trace of any such abortive 

 prophase, so that it is now doubtful whether it is normal in this species. 



A second instance of similar nuclear activity has been described by 

 Woltereck ('98) in the parthenogenetic eggs of Cypris. In the youngest 

 oocyte the chromatin is diffuse, but after a short "resting" period it col- 

 lects into strands, which contract into a dense mass at one side of the 

 nucleus. Later these strands emerge and segment into the somatic 

 number of chromosomes. Instead of proceeding further in mitosis, the 

 nuclei then undergo regression, which eventually results in their return- 

 ing to the finely reticular " resting " condition. So far as I know, these 

 two are the only accounts of any such process, for although Woltereck 

 ('98) sees a similarity in the conditions observed by Hacker ('92 b ) in 

 Canthocamptus, there is in this case a persistence of chromatin rods 

 from the last oogonial division throughout the growth period of the 

 oocyte, a state of affairs very different from an abortive mitosis. As to 

 the significance of this stage, we can conclude with Woltereck ('98) that 



