152 M. A. Giard on the Genus Entoniscus. 



handl. cler phys.-med. Gesellsch. in Wurzburg,' Bd. iii. 

 Heft 4, p. 296, pis. xvi.-xviii.). Without knowing of these 

 previous investigations, I occupied myself with the same ques- 

 tion in 1873 ; and I then gave, in the ' Comptes Rendus ' of 

 the Academy of Sciences, the description of the testis and 

 perfectly mature spermatozoids in Sacculina carcini and in 

 two species of Peltogaster. 



But in the present cases this hypothesis of hermaphrodi- 

 tism loses much of its probability, if we consider that Fritz 

 Miiller has described the male of all the species of Entoniscus 

 that he lias met with. There is very little probability that, 

 in the same genus, species so nearly allied should present a 

 physiological and morphological dissimilarity of such impor- 

 tance ; and I prefer to assume that my unskilfulness, or my 

 limited opportunities, have prevented me from meeting with 

 the males of E. CavoUnii and E. Moniezii. I need not say that 

 I have searched fruitlessly for a testicular gland, and that I 

 have observed nothing resembling the spermatozoids of the 

 Bopyrida?. 



The youngest females of Entoniscus CavoUnii that I have 

 been able to observe were in the same stage of development as 

 the young Entoniscus Moniezii, figured PI. X. figs. 3 & 4. The 

 general form was identical ; one saw the same rudiments of 

 thoracic limbs, the commencement of the formation of the 

 ventral ovigerous sac, and the two lateral ventral folds of the 

 future dorsal pouch. But there were as yet no traces of the 

 ovarian prolongations. 



As a difference of specific value between E. CavoUnii and 

 E. Moniezii at this period of evolution, I will indicate only 

 the much greater development of the first pair of abdominal 

 laminae in E. Moniezii. In Entoniscus CavoUnii the first 

 four pairs of lamina} have then nearly the same development ; 

 and it is only afterwards that the first pair grows more than 

 the others. 



III. Embryogeny. 



The anatomical details which we have just given present a 

 great number of gaps, which will be excused, I hope, by all 

 zoologists who have paid attention to the study of parasites. 

 The scarcity of materials and the obscurity of the subject are 

 two terrible obstacles, over which it is very difficult to 

 triumph. 



What we have now to say as to the embryogeny of these 

 animals is still more incomplete; and, unfortunately, long years 

 will probably be necessary to arrive at satisfactory notions 

 upon this subject. Notwithstanding the innumerable quan- 

 tity of ova which the female Entoniscus contains, it may be 



