COBBOLDj ON GYRODACTYLUS ELEGANS. 35 



would not be proven till they be found conjugating with 

 each other^ or till distinctly intermediate gradational forms 

 are discovered. 



Note on Gyrodactylus elega?vs. By T. Spencer Cobbold, 

 M.D., F.L.S., Lecturer on Comparative Anatomy, 

 Zoology, and Botany, at the Middlesex Hospital Medical 

 College. 



Mr. Bradley, F.L.S., having lately drawn the attention 

 of parasitologists to the occurrence of Gyrodactylus on Stickle- 

 backs taken from the ponds on Hampstead Heath, I have 

 recently sought for this curious genus of ectozoa on Gasterostei 

 obtained from the Serpentine in Hyde Park. 



As anticipated by the zoological editor of this ^ Journal ' (in 

 last July number, p. 196), the Gyrodactyli are not confined 

 in this country to the locality mentioned by Mr. Bradley ; 

 at least, I find them tolerably abundant on the Sticklers in 

 the Serpentine. No doubt they are common elsewhere, but 

 now that the cold weather has set in their numbers will, in 

 all probability, rapidly diminish. I have chiefly examined 

 the tails of the Gasterostei, and in proof of the truth of the 

 observation just made, I may remark that on the tails 

 of eleven fishes obtained (from beneath the Serpentine 

 bridge) on Satiu'day, the 16th of November, I found only 

 one Gyrodactylus, whereas, six Sticklebacks taken from the 

 same spot several weeks earlier, had their caudal appendages 

 almost covered with them. One fish supported several dozen 

 parasites. 



In all cases the Gyrodactyli were accompanied by numerous 

 Trichodina ; the latter being constantly present when there 

 were no other ectozoa or infusoria attached. 



Before my attention was drawn to the fact of Gyrodactyli 

 having been found in this country, I had familiarised 

 myself with the general characters of the genus from the 

 descriptions of Nordmann, Wagener, Van Beneden, Siebold, 

 and more particidarly from the observations of Wedl, whose 

 'Anatomische Beobactungen iiber Trematoden^ contains an 

 interesting appendix on the genus in question. This memoir, 

 therefore, may appropriately be added to Professor Busk's 

 list of writings on Gyrodactylus, given at p. 212 in the last 

 volume of this periodical. 



