Miscellaneous. 455 



worms remain in the uterus, moving about in all directions, pass 

 ing from one matrix to another, and increasing gradually in size. 

 They find nothing for their nourishment but the fragments of the 

 ova which they have quitted, and the mucosity secreted by the wall. 

 But this cannot suffice for them. They penetrate into the ovigeroiis 

 tube itself, wliere the ovules burst and become their prey. Finally 

 the young individuals break through the wall of the ovary, and 

 penetrate into the splanchnic cavity. This finishes the mother, 

 and she dies by being devoured alive by her progeny. The new 

 generation then quits this dead body by the mouth and the vulva, 

 only a portion of the embryos previously reaching the exterior by 

 means of a normal parturition. 



A little while before the publication of the memoir of M. Perez, 

 MM. Leuckart and Mecznikow made known some perfectly similar 

 phenomena in the Rhabditides belonging to the cycle of evolution of 

 Ascaris niyrovenosa. These observations, made nearly simulta- 

 neously but quite independently in two different countries, mutually 

 guarantee their correctness. 



M. Perez has been greatly struck by the circumstance that, under 

 certain conditions, these Rhabditides multiply for several generations 

 without its being possible to find a single male. From this he con- 

 cludes that the females of this species are fitted to reproduce par- 

 thenogenetically. We regret that M. Perez was not acquainted with 

 the observations made by M. Schneider upon his Pelodytes. In 

 these worms, which at any rate belong to the genus Rhabditis of 

 Dujardin, M. Schneider saw the females reproduce during a series of 

 generations without the presence of males. Nevertheless, a careful 

 study of these supposed females having led him to recognize the 

 normal existence of spermatozoids in the sexual nucleus, he concluded 

 that these Nematodes are hermaphrodites. Are not the parthenoge- 

 netic females of M. Perez analogous to, or even specifically identical 

 with, the hermaphrodite Pelodytes of M. Schneider ? This question is 

 particularly interesting in consideration of the dispute which has 

 lately arisen between MM. Leuckart and Mecznikow on the one 

 hand, and M. Schneider on the other, with regard to the develop- 

 ment of Ascaris nigrovenosa. The two former regard the sexual 

 Rhabditides as alternating with a generation of parthenogenetic 

 Ascarides deprived of males. M. Schneider, on the contrary, as- 

 sumes the alternation of a generation with separate sexes {Rhabdi- 

 tides) with an hermaphrodite generation (Ascarides). No doubt 

 M. Perez's memoir may be interpreted rather in M. Leuckart's sense: 

 the author has seen numerous successive generations of partheno- 

 genetic females, amongst which generations provided with males 

 were intercalated from time to time. However, as he does not seem 

 to have even suspected the existence of hermaphrodite Nematodes, 

 we may still question whether the denomination parthenogenetic 

 females which he applies to these worms is altogether above discus- 

 sion. (Thesis presented to the Faculty of Sciences of Paris, 186G, 

 pp. 156 & 5 plates ; Bibl. Univ. October 25, 1867.) 



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