524 T. H. JOHNSTON AND M. J. BANCROFT, 
This parasite was found as tiny rounded white cysts 
on the gill filaments. In all cases observed, the infection 
was extremely light. It occurred in four out of nine speci- 
mens of perch examined. In sections of an infected filament 
the cyst was seen to lie embedded in the spongy tissue, and 
in many cases occupying a relatively large area of the 
section. The cyst exhibits the usual three well defined 
layers—the outermost clear ectoplasm, an inner layer of 
developing spores, while the whole mass of the cyst within 
this is filled with mature spores. The latter appear to lie 
in a definite manner, the long axis of the spore commonly 
being at right angles to the boundary of the cyst, the 
anterior end of the spore pointing outwards. The spores, 
then, seem to radiate from the central portion of the cyst... 
The spore is greatly elongated, pointed somewhat 
anteriorly, while the posterior margin of the envelope is 
drawn out into a long tapering process or tail. When 
freshly liberated from the cyst, the tail appears single, but 
the two halves soon separate and usually diverge widely, 
giving the appearance of a double appendage. At the 
anterior end of the spore are two polar capsules which lie 
parallel and quite frequently are of different lengths, in one 
or two instances of a malformed spore they were seen to 
lie one behind the other. The posterior end of the spore 
is occupied by the amcebula containing two nuclei and a 
small vacuole. The average dimensions are:—Length of 
spore 11-15; breadth of spore 3—5y; thickness of spore 
3-4-4; length of polar capsule 5—6y; breadth of polar 
capsule 1—2py; length of tail process about 20p. 
HENNEGUYA GRACILIS DN. Sp. 
Figs. 6, 8, 10. 
Host:—Black bream, Therapon hillii Castelnau. 
This parasite closely resembles the preceding one, but 
it makes definite narrow pear-shaped cysts in the filaments, 
