144 M. A. Giard on the Genus Entoniscus. 



isolated individuals — once a female, twice a male. Each of 

 these three individuals harboured an Entoniscus, whilst none 

 were ever found in the paired individuals. Fritz Miiller con- 

 cludes from this that the presence of the Entoniscus, like that 

 of the Rhizocephala (Suctoria), superinduces sterility in the 

 animal infested, whence the abandonment of the latter by its 

 partner. 



The Entoniscus of Porcellana Creplinii differs from that of 

 the ordinary Porcellana by the colour of the ovaries and the 

 form of the ovigerous lamellae. 



3. In an Achceus living under rocks among Bryozoa and 

 Ascidia; a single couple of Entonisci ; the male, which is 

 very characteristic, allows it to be affirmed that this species is 

 distinct from E. jjorcellance and E. cancrorum. 



This, therefore, makes at least four, and perhaps five, dis- 

 tinct species of this singular genus, all inhabiting a small 

 corner of the Brazilian coast. 



It would be very odd if a group of parasites, living upon 

 animals so widely distributed as the Decapods, were localized 

 in so small a space. It may be asserted, without fear of 

 deceiving ourselves, that, when they are more carefully sought 

 for, the species of the genus Entoniscus will soon be met with, 

 more or less, everywhere. 



It was with this idea that, during a residence of several 

 weeks that I made at the Pouliguen (Loire- Infcrieure), I care- 

 fully examined many Decapods of that interesting locality ; 

 and I was especially urged to this investigation by the ex- 

 treme abundance, in the locality, of Grapsus varius, which I 

 knew had furnished Cavolini with the first species of the 

 genus Entoniscus *. 



II. Biology and Anatomy. 



The Grapsi collected in the small bays formed by the very 

 broken coast of the Pouliguen on the side of Penchateau are 

 very frequently infested by an Entoniscus which may be 

 easily recognized as identical with that described by Cavolini, 

 and which, for that reason, I propose to name Entoniscus 

 Cavolinii. 



The parasite is met with in both the males and the females. 

 According to the statistics of my researches, it is found most 



* I believe that Grapsus varius cannot go further north than the 

 mouth of the Vilaine : I do not know it beyond Piriac ; and it certainly 

 does not exist at Concarneau. We find, besides, at the Pouliguen a 

 number of southern types ; without mentioning the flora in which this 

 southern character is very strongly marked, we may cite, among insect*, 

 Argyrmis pandora, Dejopeia puicheUa, &c. &c. 



