156 M. A. Giard on the Genus Entoniscus. 



smaller than the female ; and sometimes the difference of size 

 in the two sexes is very great. Several species of Idotece 

 are remarkable in this respect. It has frequently happened 

 to me to capture these animals in the muslin net ; and almost 

 always one meets with them in couples ; the male, one third 

 or one fourth the size of the female, is placed between the feet 

 of the latter on the abdominal surface, absolutely in the same 

 position as the male of the Bopyridaj. This is the case also 

 with various Cymothoada? ; and in some species of this group 

 it is necessary, as in the Bopyridaj, that copulation should 

 precede parasitism. This occurs notably in a curious Javan 

 species described by Herklots*. 



In the course of this memoir I have several times alluded 

 to a second new species of Entoniscus, which I have also met 

 with at the Pouliguen, and which I have named E. Moniezii, 

 dedicating it to H. Moniez, preparator of zoology at the 

 Faculty of Sciences of Lille, who accompanied me in my 

 journeys on the shores of the Loire- Infeneure. 



This species appears to be very rare, since I have seen 

 only two individuals of it — an adult female and another at a 

 less developed stage (figs. 3, 4), both found in the same 

 example of Portunus piiber. This crab had been collected at 

 the island of Leven, opposite to the point of Peu-Chateau and 

 the open coast of Pouliguen. In order to find it again I have 

 in vain examined several hundreds of the Portunus fished on 

 the coast. 



I have already indicated above some differences between 

 this species and that of Cavolini in the stage represented 

 (figs. 3, 4). 



The adult individual unfortunately contained only slightly 

 developed embryos ; and I was unable to compare these 

 embryos with those of the species from the Grapsus. The diffe- 

 rential characters were furnished to me by the colour of the 

 ovary and of the ovigerous sacs — peculiarities of which Fritz 

 Miillcr ought to have made use to distinguish the various En- 

 tonisci parasitic on Porcellanos. In E. Moniezti the ovigerous 

 sac is of a nankeen-yellow, instead of presenting the greyish- 

 yellow colour of E. Gavolinii at the same grade of evolution 

 of the eggs. The ovarian gland is yellow with a rosy tint ; 

 it is straw-yellow in the parasite of the Grapsus. 



* J. A. Herklots, " Deux nouveaux genres de Crustaces vivanten para- 

 sites des poissons : Epicthys et Icthyoxenos," Archives Neerlandaises, 

 tome v. 1870, p. 120 (Icthyoxenos Jellinyhausii). 



