46 
ON MYXOSPORIDIA IN FLAT-FISH. 
By H. M. Wooncock, B.Sc. (Lond.). 
Myxosporidia are Sporozoan parasites frequently 
found in fishes generally, and often the cause of severe 
ee 
disease, e.g., the “ Pockenkrankheit ’ of carp, and the 
‘ Barbenseuche”’ of the barbel, which have at times 
ravaged these fish in continental rivers. 
The group is characterized (a) by the fact that repro- 
duction by spores goes on throughout the growing or 
“trophic ” period, and (6) by the complicated process of 
spore-formation and the nature of the spores. ‘These con- 
tain, besides the germ or ‘ sporozoite,”’ one or more 
‘ polar-capsules ” (very similar to hydrozoan nemato- 
cysts), from which filaments—serving as organs of attach- 
can be extruded. 
ment to the epithelium of the new host 
Until recently the Pleuronectidie were thought to be 
immune to the attacks of these parasites, and, in fact, 
to-day, there is, so far as IT am aware, only one paper which 
specifically describes their occurrence, and at most two or 
three which record cases of disease in flat-fish either cer- 
tainly or probably to be ascribed to infection by 
Myxosporidia. 
In 1899 tagenmiiller (2) gave a short account (un- 
fortunately without any figures) of a Myxosporidian 
infecting Flesus passer, Moreau (= Pleuronectes flesus, the 
flounder), a common member of the fauna of brackish, 
littoral pools in the neighbourhood of Endotime. At least 
fifty per cent. of the specimens captured harboured the 
parasites, which turned out, on investigation, to be a new 
species of Nosema (Glugea), to which Hagenmiiller gave 
the name V. stephani. This genus belongs to the sub-order 
Cryptoeystes (Microsporidia), comprising forms which 
