328 Prof. A. Giarcl on Parasitic Castration 



erroneous, for it seemed to have a relation to another fact of 

 the same nature long since indicated in the case of other 

 parasites. As long ago as 1837 Rathke wrote : — " Mirabile 

 dictu, Bopyri omnia quse vidi exempla — yidi autem eorum 

 plures centurias — solnmmodo in Pala^monibus feminis repe- 

 reram, licet in raanus meas non pauciores hornm animalium 

 mares, quam feminse incidissent " (' De Bopyro et Nereide/ 

 p. 18). Choice in fixation does not seem to be theoretically 

 more impossible in the case of the SaccuUnre than in that of the 

 Bopyri. 



However this maybe, for several days I carefully examined 

 the numerous Stenorhynchi which every sweep of the trawl 

 brings np from the bottom of the Bay of La Forest. At the 

 first glance the superficial examination that one could make 

 ©n board the boat seemed fully to confirm Fraisse^s opinion. 

 On the first day of dredging I returned to the laboratory quite 

 convinced that I brought back only female Stenorhynchi 

 bearing Sacculhue. This crab is so transparent that, even 

 without lifting the tail, we can perfectly distinguish the 

 yellowish tint of the parasite through the integuments of its 

 host. 



As in Stenorhynchus the number of males greatly exceeds 

 that of the females, the apparent immunity of the former 

 became still more singular. But a careful examination of 

 these Crustacea soon revealed some very curious facts, although 

 very different from that indicated by Fraisse. 



In the infested females the influence of the parasite, which 

 displays itself internally by the abortion of the ovules, betrays 

 itself externally by a profound modification of the four pairs 

 of ovigerous feet on the abdomen. These appendag-es are 

 very inferior in size to the normal state, sometimes reduced to 

 small scarcely plumose arcs ; and we cannot ascribe their 

 atrophy to wearing caused by the friction of the Sacculina. 

 In fact, I have ascertained that in adult females upon which 

 the recently evaginated SaccuUna was still of very small size 

 and removed from all contact with the ovigerous feet, the 

 latter already presented the dwarfish and stunted aspect of 

 aborted organs. Here therefore there is no mechanical action, 

 but a remarkable fact of correlation of growth. 



I soon observed infested Stenorhynchi, apparently quite 

 similar to the preceding, in which the ovigerous feet did not 

 exist at all ; but in these cases it was easy to find, between 

 the parasite and the sternal surface of the crab, the copulatory 

 styles, greatly reduced in size it is true, and, further, the posi- 

 tion of the genital apertures was difterent. In one word, 

 these individuals were males in which the tail had the width 



