Sl’UDIES IX THE EXPERIMENTAL ANALYSIS OF SEX. 279 ^ 
tliat Peltogaster would stimulate the glycogenic function of 
the liver, and lead to an excess of glycogen being formed 
which could be utilised for the moult, while Sacculina would 
inhibit glycogen formation and inhibit moulting in conse- 
quence. Unfortunately this hypothesis will not stand the 
test of experiment, for sections of the roots of Sacculina and 
of Peltogaster stained with iodine do not show in either case 
a trace of the presence of glycogen. 
Potts (6) has given a simple mechanical explanation of the 
reason why infected Pa'gurids moult while Carcinus and other 
crabs do not, this explanation being that the Sacculina acts 
as a mechanical rivet on the comparatively hard tissues of the 
crab, while Peltogaster, being attached to the soft-bodied 
abdomen of the Pagurid, does not prevent the old skin from 
breaking away and being shed. It seems, however, that this- 
can hardly be the true explanation, since the mere presence 
of a mechanical rivet would not prevent the crab from growing 
and forming a new skin underneath the old one and of grow- 
ing until it burst. There must surely be some physiological 
cause at work in the case of crabs infected with Sacculina 
wliich inhibits glycogen storage, growth and moulting. 
Whether this cause is active or not in the case of Pagurids 
infected with Peltogaster we cannot say for certain, but in 
the next section we shall call attention to certain facts which 
prove that growth and moulting* are not necessarily connected 
processes, that moulting may take place without growth, and 
that in this case there is probably a lack of reserve material 
which prevents growth, although it may not prevent moulting. 
In the case of Pagurids infected with Peltogaster, it seems 
certain that the frequent moulting is not accompanied by 
active growth, because, if it were, infected individuals should 
on the average be larger than normal, and this is emphatically 
not the case. 
We shall return to this subject after the quantitative 
results on glycogen formation have been given in the next 
section. 
