e 
ay) 
Plea 
" 
fon 
= i a) ian ia 
Ee ete a ee eee ee a EM ie AE met 
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 ovigerous 
tube itself, where 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 nigrovenosa. 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 Rhadbditides 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 Jed 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, 1866, 
pp. 156 & 5 plates; Bibl. Univ. October 25, 1867.) 
31* 
