BY DAVID G. STEAD. 



689 



rifrons as recorded by Prof. Haswell. Prof. Giard, in speaking 

 of a SaccuJina parasitic upon Steitorhynchus j)/talanginm, says : — 

 " In the infested females the influence of the parasite . . . • 

 betrays itself externally b}' a profound modification of the 4 pairs 

 -of ovigerous feet. These are very inferior in size to the normal 

 state." 



As before stated, in the present case no such modifications as 

 the foregoing have taken place. 



In some specimens there was a slight difterence in the form of 

 the pleon. This unimportant difterence, consisting as it did of a 

 slight narrowing, could not in any wa}' be attributed to the 

 parasite, as the same could be found in specimens which had not 

 been attacked by the Sacculina. 



As would be expected, it is quite evident that the parasites 

 prevent their hosts from reproducing their young, as no signs of 

 ova were to be seen on attacked females, although at the time 

 that I procured my specimens it was the breeding season, and 

 many ovigerous females could be found roundabout. 



As will be seen by referring to the following 12 examj^les 

 taken indiscriminately, the parasites do not alwa3's attack the 

 same part of the pleon, nor do they favour especially either sex. 



Sitiialion of Sacculina. 

 On right side of intestinal canal under 3rd segm. 



(Same width as host.) 

 On right side of intestinal canal under 5th segm. 

 Middle of intest. canal under .3rd segm. 



4th 



4tll 



This had been attached to the junction of pleon and 

 pereion, but had been dislodged —whether by its 

 host or accident, I know not — before the crab came 

 into my possession. 

 $ ... 1 ,, ... On left side of intest. canal under 4th segm. 

 Q 6 ,, ) ••• Both together on the middle of intest. canal under .3rd 



6 ») segm. These two .S'ac'c?//ui('' — as larvaj — must have 



gone "hand-in-hand," as they were both attached 

 to same spot, and were also of the same size. 



