Miscellaneous. 347 



teuce of some species of this genus on the shores of the Loire-Infe- 

 rieure, and to make known some new peculiarities of their degraded 

 organization. 



The commonest species occurs under the carapace of Grapsus mar- 

 moratus, Fab. (varins, Lat.), a crab which is very abundant on 

 the rocks of Pouliguen. I shall call it Entoniscus Cavolinii, as it 

 seems to be very probable that Cavolini saw the female of this 

 species and described it as a gall produced on the viscera of the 

 Orapsus (Granchio depresso, GrancMo spirito) by the oviposition of 

 the Oaiscus squill if or mis, which is simply the young of the En- 

 toniscus at the moment of its escape from the ovigerous sac*. 



Entoniscus Cavolinii differs considerably from the two species 

 studied by Fritz Miiller. The fringed laminae, so highly developed 

 on the ventral part of the thorax of Entonisctis por-cellancef, do not 

 exist here ; nor do we find the sword-shaped abdominal feet. These 

 two characters approximate our species to Entoniscus cancrorum, 

 the parasite of Xantho. But while in the latter the abdomen has 

 a continuous undulated fold only on each side of the first two seg- 

 ments, we find in E. Cavolinii five pairs of lamellar appendages, 

 folded and undulated, corresponding to the five pairs of ramified 

 appendages of the abdomen in lone. These appendages diminish 

 towards the extremity in such a manner that in appearance the 

 first pair forms two large lateral tufts, and the following four a 

 median posterior tuft, equivalent to each of the fii'st two. The 

 ovary presents four lateral prolongations, two anterior and two 

 posterior, besides two or three pairs of less-visible eminences, no 

 doubt corresponding to the thoracic feet which have disappeared ; 

 it also presents two long median dorsal prolongations. Analogous 

 lobes are observed on the female of the Cnjptothiria halaniX. 

 These lobes, which are very regular and constant, were not seen by 

 Fritz Miiller. I believe that those of the dorsal parts recall mor- 

 phologically certain features of the Zoea-iorm.. 



The embryo likewise presents very clear differential characters. 

 The front is nearly straight, as in Entoniscus porcdlance-. Besides 

 the lateral eyes, which are double and correspond to the definitive 

 eyes of the normal Isopoda, it possesses a median eye, formed by two 

 contiguous crystallines, some pigment, and optic nerves. It is the 

 J^auplian eye that has persisted, with a structure identical with 

 that which it presents in a multitude of Copepods ; and it disappears 

 afterwards, together with the secondary eyes, in the retrograde 

 metamorphosis of the female Entoniscus. This fact appears to me 

 of great importance, as indicating a trace of the Nauj^Uus phase in 

 the ontogeny of the Isopoda. Each of the first five pairs of thoracic 

 legs terminates in a prehensile hand, the penultimate joint of which 



* Cavolini, Memoria sulla generazione dei Pesci e dei Granclii. Napoli, 

 1787, p. 180 et srqq. 



t See Ann. & Mag. Nat. Hist. ser. 3, vol. x. p. 87 (1802). 



\ I have been able to examine this curious para^site at Wimereux, 

 where it is met Avith from time to time in Balaniis haUmoides. 



