326 Prof, A. Giard on Parasitic Castration 



bedding and sectioning, describing as closely as possible a 

 microscopic preparation, detailing to the public the little 

 misadventures of a badly-conceived histological cuisine are 

 the- things which constitute a jjresentable thesis ; as to the 

 conclusion of the memoir, that must be impressed with the 

 greatest reserve. It will be remarked, for example, that the 

 Brachiopoda are probably Brachiopoda, and that, in spite of 

 all the recent works upon the Tunicata and the Bryozoa, the 

 subkingdom MoUusca is still extant. And nevertheless the 

 enormous mass of facts which is every day being accumulated 

 by the naturalists of the whole world renders more and more 

 necessary the employment of the synthetic method, without 

 which science is a chaos. Moreover, theoretical ideas, far 

 from being, as has been asserted, a source of error, very often 

 enable us to correct old erroneous and imperfect views, and 

 to render available peculiarities which, without them, would 

 have passed unnoticed. 



The present note, I think, will be a fresh demonstration 

 of the aphorism enunciated by Prof. Marey. 



I. 



In the course of last summer, at Conearneau, I had the 

 opportunity of studying a ISaccuIina parasitic upon Steiio- 

 rhynchus i)lialangium^ Pennant. This Sacculina had already 

 been indicated, without description, by Fraisse, who met with 

 it at Naples ; 1 called it Sacculina Fraissei, in honour of that 

 zoologist. It appears to be rather common. Although such 

 statistics are very liable to vary and only constitute the 

 resvilt of a rough approximation, I estimate at about one in 

 iifty the number ot Stenorl/ynchi infested by this Rhizo- 

 cephalan among those captured in the Bay of La Forest. 



Sacculina Fraissei is easily distinguished from the other 

 species of the same genus by its external form and its organi- 

 zation. It is entirely concealed in the sort of case formed by 

 the tail of the crab and the sternal plastron. Its outline is 

 cordiform. The cloacal aperture is nearly sessile, and irre- 

 gularly triangular in young individuals. The chitinous ring 

 which surrounds the peduncle is very simple and not strongly 

 marked ; the peduncle is hollow ; the roots are thicker and 

 more irregularly branched than those of S. carcini ] the col- 

 leteric glands annexed to the ovary are well developed and 

 situated at the sides, towards the upper third of the height. 

 The orientation is the same as that of S. carcini. The 

 ovoid, or nearly spherical, testes are situated at the median 

 part of the posterior half of the ovaries, nearly in the centre 



