1873.] 179 [McCrady 



which extended completely round the body. 1 The only permanent 

 transverse constriction I observed was that separating the tentaculi- 

 ferous extremity from the rest of the body. Finally the rigidity of 

 the tube seems to separate this species from B. Haimeanus, and to 

 approximate it to B polymorphus] an approximation borne out by 

 the presence of those bodies in the tentacula which reminded me of 

 lasso-cells; something like which seem to be present in Baer's fresh 

 water species, but not in the B. Haimeanus, though the latter, like 

 our B. cuculus, belongs to the sea, and is found in the oyster (Ostrea 

 edulis) of Europe, as B. cuculus is in 0. Virginiana. 



The appearance of the oysters infested by this parasite is precisely 

 that described by Lacaze-Duthiers. Instead o$ the creamy or yel- 

 lowish tint of the healthy ovary, this part of the animal, on removing 

 the shell, seems covered by a transparent tissue, beneath which are 

 seen indistinctly the branching tubes, which in this position have 

 rather a brown appearance, a^d do not appear white, as they seem 

 when removed from the organ. According to my observations, the 

 whole generative organ is filled by the branching growth of this 

 sporocyst, but I did not observe the parasite in any other part of the 

 body. Moreover, in such oysters, though not specially sickly in 

 appearance, and only less fat than their healthy companions, I did 

 not find any trace whatsoever of either ova or spermatozoa; and I 

 understand the presence of this parasite as completely destroying, for 

 the time at least, the fertility of its victim. It is quite conceivable 

 that the years of short spawn, said to be frequently noticed by those 

 concerned in oyster culture, may be due to unusual abundance of 

 these parasites in those years. I had no means of ascertaining 

 whether the parasite proves fatal to the oyster. As I have said, no 

 very distinct signs of sickness are observable. Of the oyster, from 

 whose reproductive organ the parasites sketched in figs. 7 and 8 were 

 taken, I find the following remark in my journal, " This oyster was 

 taken out of the mud yesterday morning" (July 29th, time of wri- 

 ting), " and stood all day and all night upon my microscope table 

 without water, but in the shade." In the summer of Charleston this 

 is a severe ordeal for a healthy oyster, yet the next sentence records : 

 " His heart was beating, and he seemed in pretty good condition not- 

 withstanding this treatment. He was not, however, so fat as many of 

 the oysters are even at this time, and an examination of the genera- 



1 By an error in the woodcutting, one of the constrictions in Fig. 6 does appear 

 to be continuous across, but this is not the case in my original drawing. 



