; 51 
different from the true cysts in Johnstone’s plaice, which 
I will call in future specimen A. Before describing the 
two varieties minutely, it will, perhaps, help to understand 
their structure, to give briefly the course that the develop- 
ment of the parasites has followed in the two cases. 
In both, the infection is a ripe, well-matured one, but 
whereas in A it is very strong, and must have proceeded 
from a great number of centres (in other words, the host 
swallowed very many spores), in my plaice (B) it is only 
a slight one. Perhaps this supplies, at any rate partly, 
the reason for the fact that here the individual parasites 
have tended to spread the infection further, invading the 
neighbouring tissue of the host largely by the process of 
endogenous multiplication (‘ multiplicative reproduction ” 
of Doflein (1)) in the young forms. Indeed in the case of 
Glugea, where cell-infection prevails, this condition of 
diffuse infiltration is, to a very considerable extent, the 
result of endogenous reproduction, and, therefore, ap- 
parently differs rather in origin from the condition 
as it is generally understood to occur in the larger Myxo- 
sporidia; although I think it is by no means unlikely that, in 
these also, it will be found that endogenous reproduction 
has a larger share in the result that is at present ascribed 
to it, for Doflein (l.c.) describes in one instance (J yrobolus 
cyprini, the cause of “ Pockenkrankheit ”’) a similar multi- 
plicative reproduction of young forms while still intra- 
cellular. There is, therefore, no need to restrict, as he 
would, the term diffuse infiltration to such larger forms, 
which, when adult, are intercellular. Thélohan, in first 
describing the condition, was not aware of this endogenous 
reproductive capacity, and looked upon it as a more or less 
continuous ramifying infiltration of the parasitic body, 
with displacement and disturbance of the surrounding 
tissue. Whereas, as we have just seen, it is far more 
