F. A. Potts 
43 
occasioned considerable controversy among the distinguished investi¬ 
gators of the problem, but extraordinary as are the proved changes 
which Sacculina undergoes in its development, yet another phenomenon 
results from its association with its host which is certainly of equal 
importance. It is of no small interest then, that while to Delage we 
owe the clear and convincing demonstration of the endoparasitic 
development of Sacculina, it is Alfred Giard, whose recent death we 
all deplore, who gave the first description of the effects that the same 
parasite causes in the reproductive system of the Crustacea it infects. 
Abdomens of Shore Crab ( Carcinus ) infected by Sacculina. 
Fig. 1. 
In 1877 Fraisse was engaged on the study of the Sacculina 
parasitic on the spider crab ( Inackus ). In a paper published in that 
year he calls attention to the fact that the males of the infected species 
never harbour the parasite, and this he attributes to their narrow' 
abdomen forming but an insecure lodgment for an attached organism. 
This iustance of the sage discrimination of the infant Sacculina when, 
at the end of its free-swimming life, the time comes to choose a foster¬ 
parent, was refuted by Giard, who pointed out that the real reason of 
this apparent immunity was to be found in the tendency for the males 
attacked by Sacculina to exchange, at the moult subsequent to infec¬ 
tion, their narrow abdomen for a broader one approaching the female 
type. He also remai’ked that the swollen chelae characteristic of the 
adult male spider crab are represented in the parasitised form only 
by the attenuated pincers usually associated with the female sex. For 
these reasons Giard considered it unnecessary to figure a crab of this 
kind, for “ it w’ould be indistinguishable from the classical figures of the 
female sex.” Besides this well-marked effect in the infected male 
the French observer detected an equally definite assumption of male 
