32 M. J. de Guerne on the 



apparatus, which seems to vary veiy little in the same species. 

 Moreover the raastax, which resists the digestion of certain 

 fishes to such an extent that it may be recognized in their 

 intestine, may serve to determine the types obtained by dis- 

 tant fishings and mounted on the spot. It wiW often happen, 

 however, especially in the case of pelagic faunas, that the 

 Asplanciince will occur in great numbers and that it will be 

 easy to break up many specimens for the purpose of study. 



The dichotomic table will have to be kept up with the 

 progress of science. It is possible that future discoveries will 

 compel us to transfer from the first division into the second 

 the species of which the male is unknown. At present, I 

 assume, until there is evidence to the contrary, that all the 

 forms of which the female alone is described have globular 

 males destitute of appendages. 



It will be observed that I have not introduced into the 

 table either Asplanchna intermedia, Hudson, and A. trioph- 

 tlialma, Daday *, which are not well defined, or A. mjjr- 

 meleo, Ehrenb. This last, it seems to me, must be taken as 

 the type of a new generic group, which I will name Asplanch- 

 nopus. This name, like the separation of the genus, is 

 founded upon the remarkable peculiarity presented by A, 

 myrmeleo of the possession of a foot. The presence of this 

 rudimentary organ seems to indicate in this Rotifer a less 

 advanced degree of adaptation to a pelagic life than in the 

 true AsplanchncB. From this point of view it would present 

 some analogy with Notops. The male has not yet been met 

 with. It would be the more interesting to ascertain whether, 

 like the other sex, it has retained a vestige of the foot, 

 because all the males of the class are singularly atrophied. 



* Hudson, *' On some Male Rotifers," in Monthly Micr. Journ., Feb- 

 ruary 1875, p. 53, pi. xci. fig. 7, and Hudson & Gosse, loc. cit. vol. i. 

 p. 122, note. Von l)aday, " Neue Beitrage zur Keuntniss der Rader- 

 thiere," in Math. u. naturwiss. Berichte aus Ungarn, vol. i. p. 263 (1883). 

 The following is the diagnosis of A. triophthalma : — " Corpus truncato- 

 ovatuni ; ocellis tribus, duobus marginalibus, una maj ore collari ; organo 

 rotatorio simplice, parum undulato ; fronte organis tentaculatis ; pede 

 anoque caret. Longit. corp. 0'"™-8-l'"'"-2." 



According to the author this Rotifer, one of the largest known, would 

 closely resemble A. Sieboldi, Leyd. ; the male, however, is globular. Von 

 Daday gives no particulars as to the mastax. Its locality is Mezo-Ziih 

 (Hungary ?). 



It will also be remarked that no mention is made of A. Boicesi, Gosse. 

 Even according to the naturalist who has described it, this species does 

 not differ from A. BvujhtioelU (Gosse, " A Catalogue of Rotifera found 

 in Britain," in Ann. & Mag. Nat. Hist. ser. 2, vol. viii. p. 200). 



