t924. Southern. — The Fauna of a Hatchery Filter. i-^y 



Hydra vulgaris Pallas, was extremely abundant on the 

 walls and bottom of the compartments. Swimming about 

 in the water were numerous specimens of the cope pod Cyclops 

 vulgaris Koch/ mostly bearing egg-sacs, and a few 

 immature water-mites. Several specimens of a small 

 cladoceran Chydorus sphaericus O. F. Miiller, and of the 

 fresh-water shrimp Gammarus ptilex (L.) were noted. In 

 the mud at the bottom of the filter were numbers of large 

 oligochaetes belonging to the species Lumhriculns variegatus 

 Miiller, very numerous specimens of a Chironomus larva 

 living in long mud-covered tubes, and a few other insect 

 larvae. A single specimen of the hair-worm, Gordius sp., 

 doubtless introduced by some insect in which the larval 

 stage is parasitic, was found, but the species to which it 

 belonged was not determined. 



In the forest of Cordylophora stems lived large numbers 

 of oligochaetes. The common and widely spread species 

 Stylaria laciistris (L.) was very abundant, and a few 

 specimens of a rarer form. Chaetogaster diaphanus (Gruith.) 

 were observed. 



Floating on the surface of the water was a single specimen 

 of a large ephemerid having a close superficial resemblance 

 to a Mayfly. It has been examined' by Mr. M. Mosely 

 and named by him Siphlurus armatus Eaton. This species 

 has been found in various parts of Great Britain, and 

 there is a single Irish record, from Killarney, but the species 

 has apparently not yet been observed on the continent. 

 This large and conspicuous insect would undoubtedly be 

 called a Mayfly by anglers who were not experienced 

 entomologists, and its presence in Ireland indicates the 

 necessity of regarding with caution statements of the 

 occurrence of Mayflies on waters where, for various reasons, 

 one would hardly expect to find them. 



Department of Fisheries, Dublin. 



1 I am indebted to Mr. A. C. Ciardiner for the correct identification 

 of this species. 



