126 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



ON MYXOSPORIDIA IN FLAT-FISH. 

 By H. M. Woodcock, B.Sc. (Loud.). 



Myxosporidia are Sporozoan parasites frequently 

 found in fishes generally, and often the cause of severe 

 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 (b) by the complicated process of 

 spore-formation aiid 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- 

 ment to the epithelium of the new host — can be extruded. 



Until recently the Pleuronectidse were thought to be 

 immune to the attacks of these parasites, and, in fact, 

 to-day, there is, so far as I 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 Hagenmuller (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 Endoume. 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 Hagenmuller gave 

 the name N . stephani. This genus belongs to the sub-order 

 Cryptocystes (Microsporidia), comprising forms which 



