1901. I5S 



SOME IRISH SPECIES OF FRESHWATER HYDRA, 



BY A. H. TOPPIN. 



There have been very few records of the freshwater Hydra in 

 Ireland of late years, and it maybe of interest to some readers 

 to know that both brown and green species occur in the 

 County of Dublin. The latter was obtained last year by Mr. 

 Halbert in some quarry-holes near Crumlin, Co. Dublin ; while 

 Mr. F. M. Sellens found, in a pond at Sutton, Co. Dublin, 

 both Hydra viridis and H. fiisca, which he exhibited to the 

 Dublin Microscopical Club (i, p. 95) Thompson (2, p. 459), 

 distinguished four Irish species of Hydra, viz. : — H viridis, 

 Linn. ; H viclgaris, Pall. ; H. fusca, Iyinn. : and H verrucosa, 

 Templeton ; but as has been observed by Allmau (3, p. 328), 

 H verrucosa is probably identical with H. fusca, while the 

 name H grisea, Einn., being older, should stand for H vulgaris, 

 Pallas. 



About the beginning of May last, I obtained some speci- 

 mens in a pond near Eoughlinstown, Co. Dublin, which seemed 

 to agree in most of the characters with H grisea. They 

 varied in colour from an orange-brown to a pale yellowish- 

 brown, and in one case perfectly white ; but this might have 

 been due to confinement for a considerable number of days. In 

 each specimen the body was cylindrical, and ranged from five 

 to seven mm. in length. The tentacula, six to eight in 

 number, were as long as, or rather shorter than the body ; but 

 in one specimen, when the body was contracted, they were 

 longer. The thickest part of the body appeared to be the 

 middle, and it gradually tapered towards the mouth and base, 

 and, therefore, differed in shape from H fusca. At the anterior 

 end, the body broadened out, forming a kind of oval-shaped 

 head surrounded by the tentacles. . 



All the specimens which I examined seemed to agree with 

 H. grisea in shape, colour, and length of tentacles, but not in 

 number, as H. grisea possesses from seven to twelve, whereas 

 all my specimens never had more than eight (the white 

 specimen having six only). In this respect they seemed to 

 accord with H.Jusca, but differed entirely from that species in 

 all other characters. 



