M. A. Griard on the Genus Entoniscus. 151 



embryos, which, like the ova of all the other Crustacea, need, 

 for their development in the incubatory cavities, perfectly 

 aerated water. It is only necessary to place a female of Bopy- 

 rus, separated from her host, in a glass filled with sea-water, 

 even very pure and renewed several times a day, in order to 

 see that the development of the ova, contained under the ven- 

 tral lamella?, is soon arrested. 



We have given above the description of the ovary. It will 

 be sufficient to add that near the aperture of tlie ventral ovi- 

 gerous sac we find two colleteric glands, the secretory ducts 

 of which open not far from the apertures of the ovary near 

 the small ventral eminences (PI. X. figs. 7 & 2). These 

 glands no doubt secrete the shell of the egg. There are 

 analogous glands in Hemioniscus. 



Notwithstanding careful search, I have been unable to 

 meet with the male of either of the two species of Entoniscus 

 that I have observed. I have vainly sought for it upon the 

 body of the female and upon the crab parasitized. The notion 

 that these Entonisci may be hermaphrodites evidently presents 

 no absurdity a priori. In fact we are acquainted with her- 

 maphrodite types in certain zoological groups which are 

 composed principally of forms with separate sexes. Speaking- 

 very generally, parasitism, or even fixation (which is only a 

 first degree of parasitism) , pretty frequently induces the deve- 

 lopment of the two sexes in the same individual (Cirripedes*, 

 Ascidia, Acephala). 



As long ago as 1866 Kowalevskyf observed the testes 

 and the mobile spermatozoids of a fine Peltogaster parasitic 

 on Callianassa subterranea, and since described by Kossmann 

 under the name of Parthenopea. He states, in the memoir, 

 that he has met with hermaphroditism in several other species 

 of Peltogaster and Sacculina. 



Kossmann, in a memoir upon the Suctoria, has also figured 

 (in 1872) the spermatozoids of several species, but did not see 

 the mobile form of those elements. Kossmann's memoir was 

 first published in a journal which is not much diffused (' Ver- 



* The hermaphroditism of the parasitic Cirripedes of the group Suc- 

 toria or Rhizocephala was long in doubt in consequence of the numerous 

 errors which have been published on this question. It is not very long 

 since Hesse described as the male of Peltogaster a Bopyride Isopod 

 crustacean ! Such fancies would not deserve to be noticed here if they 

 had not acquired a certain importance, even in foreign countries, by the 

 support they have met with from certain Parisian savants. It is not 

 without astonishment that we find a man of the importance of Spence 

 "Bate still asking in L878. " What do we know of the male of the Suc- 

 toria?" (Ann. & Mag. Nat. Hist., June L878). 



t Rippenquallen, see note, p. 149. 



