142 M. A. Giarcl on the Genus Entoniscus. 



the trouble to demolish errors which did not exist in the 

 authors incriminated, and to rediscover truths which had long 

 been known 



Thus, quite recently, in his interesting memoir on the 

 genus Cryptoniscus, P. Fraisse (2, p. 41) *, giving an analysis 

 of the memoirs of Cavolini, makes the Italian naturalist say 

 that it is very difficult to separate the Entoniscus (the sup- 

 posed ovigerous sac) from the viscera of the crab. It is 

 evident that if Fraisse had had the text of Cavolini before 

 him he would not have translated " questo corpo non e diffi- 

 cile separare " by " er sagt (Cavolini) dass er sehr schwer zu 

 trennen sei." 



I am equally unable to understand why Fraisse (I. c. p. 41) 

 reproaches Steenstrup with having falsified the sense of Cavo- 

 lini's observations, saying that the Isopods observed by the 

 latter were in the Sacculina and not in the body-cavity of 

 the crabs. The following is, in fact, the very judicious 

 appreciation, given by Steenstrup, of the facts observed by 

 Cavolini : — 



" Among the excellent observations," he says, " contained 

 in the valuable memoir of Cavolini, we find figured a very 

 curious mass of irregular form entirely filled with more or 

 less developed ova. This mass was found in a crab ; by one 

 of its extremities it was fixed to the inner stomachal wall,- by 

 the other it was fixed between the two partitions which bound 

 at the sides the segments forming the thoracic cavity of the 

 crab. In fig. 18, m, n, Cavolini has represented ova taken 

 in the mass in various stages of development ; in fig. 18, r r, 

 he has figured two young animals at the moment of their 

 issuing from the egg. Cavolini compares these young ani- 

 mals to the Oniscus sqailliformis described by Pallas, and 

 designates them by that name. It is impossible not to recog- 

 nize in the description and drawing of these embryos a form 

 very nearly allied to the Liriope of Ilathke, so near that one 

 can hardly separate it therefrom ; one is consequently led, in 

 spite of one's self, to a comparison with the larvte of Bopyrus. 

 The form of the young therefore shows us that this mass 

 tilled with ova is, in all probability, nothing but a degraded 

 crustacean parasite, and even an animal of the family Bopy- 

 ridce ; only the animal is still more deformed, and, one might 

 say, more monstrous than any other type of Bopyride, and even 

 then Peltogaster and Pachyhdella. It is more than an Epi- 

 zoon : it is an Entozoon, a sort of intravisceral worm, since, 

 like the singular Gasteropod (EntoconcJuc mirabilis) disco- 



* These references throughout indicate the works of which a list is 

 given at p. 157. 



