104 bulletin: museum of comparative zoology. 



amounts to a synapsis in every cell di\'ision, so that in many cases the 

 figures closely resemble the haploid groups. Apparently this takes 

 place especially in early prophase, but a second conjugation may 

 occur dm'ing metaphases, just a short time before division. In the 

 second, or metaphase, conjugation, at least, it is worthy of note that 

 the union is unquestionably a side-by-side or parasynaptic one." 

 Thus we find parasynapsis in a greatly exaggerated form in these 

 examples from the Diptera. 



Of recent studies on Vertebrata, we may note those of Snook and 

 Long on an amphibian, of Jordan on an opossum, and of Wodsedalek 

 on the pig. 



Snook and Long ('14) find the same kind of evidence for para- 

 synapsis that has been presented for Batrachoseps by Janssens ('05), 

 for Salamandra by the Schreiners ('07), and by Wilson ('12) as quoted 

 at p. 102. This evidence, together with that announced by Mont- 

 gomery ('11) for Plethodon, forms a series of observations which 

 renders very probable a general occurrence of parasynapsis among 

 amphibians. 



Jordan ('11) describes in the spermatogenesis of an opossum what 

 he considers evidence for telos;vTiapsis. His figures, however, are far 

 from convincing on this point, since they could as readily be inter- 

 preted in favor of parasynapsis as telosjaiapsis. 



Wodsedalek ('13), in his studies of the spermatogenesis of the pig, 

 is unable to find conclusive evidence on the subject of synapsis. He 

 says (p. 13), however, that in the synezesis stage, "The thin tlireads 

 become arranged in a very much tangled mass of loops, which later 

 appear in about half the original number and twice as thick." Inas- 

 much as these phenomena accompany every case of demonstrated 

 parasjTiapsis, the evidence seems to favor the occurrence of this mode 

 of conjugation in this case. 



In conclusion, I think it must be admitted that there is abundant 

 evidence for a widespread occurrence of parasynapsis, especially as 

 shown by the most recent investigations. While a majority of the 

 authors who have worked on orthopteran material have reported 

 telosynapsis, I believe there is some chance that many of them were 

 mistaken, or that a more careful analysis of the critical stages would 

 have given a different result. Whether we accept the hypothesis of 

 Stevens, that all degrees of s\Tiapsis occur, or the idea of Gregoire, 

 that parasynapsis is an almost universal phenomenon, we must at all 

 events admit that the most careful of the recent investigations indi- 

 cate that the latter condition is widespread throughout the animal 

 kingdom. 



