110 MK. TRANCIS DAT OK 



On some Irisli Gasterostei. 

 By Fbancis Day, F.L.S., T.Z.S., &c. 



[Eead NoTember 2, 1876.] 



The following short remarks on some Irisli Sticklebacks are 

 based upon a small collection of fisli which I made in June this 

 year whilst with Dr. Dobson at Edgewoi^thstown (county of Long- 

 ford), Ireland. 



My attention had been drawn to Dr. Sauvage's interesting revi- 

 sion of the family Gasterosteidse (' Nouvelles Arch, du Mus. 

 d'Histoire Naturelle,' 1874), which I had with me, and wherein 

 he augments the species resident in Europe from seven (as given 

 in the ' Catalogue of Fishes of the British Museum ' in 1859) to 

 seventeen. Dividing the genera into three subgenera, he at- 

 taches considerable prominence to the presence or absence of 

 plates along the sides, whilst the character of the pubic bone is 

 deemed of sufficient importance to form a subgenus upon it. I 

 wished to test his conclusions by fresh specimens ; and if results 

 tend to throw doubt upon some of his admitted species, it must 

 be remembered that my facts have been collected subsequent to 

 the publication of the memoir alluded to. 



Abnormal variations of form or structure in single specimens, 

 of course, are not of the same importance in zoology as abnormal 

 variations or varieties of species due to local influences. The 

 Jirst may be accidental, as owing to injury in the specimen ; the 

 second has some local cause at work, the action of which is more 

 or less apparent in the whole of the members of the species. When 

 such local effects can be ascertained, they are interesting; where 

 the cause can be shown, doubly so ; for a local cause may have a 

 wider signification than is at first apparent. 



Some fishes doubtless show a greater proclivity to abnormal de- 

 viations from the original type than others. Thus the Perch {Verca 

 fluviatilis) is not considered to be subject to any considerable va- 

 riation in the normal number of its dorsal spines and rays ; on the 

 other band, the contrary is observable in the majority of the East^ 

 Indian freshwater Acanthopterygian forms. 



Much stress has been laid in ichthyology on the presence or 

 absence of ventral fins. Irrespective of the apodal fishes, we 

 have, amongst the Acanthopterygians in the family Ophiocepha- 

 lidse, the genus Channa, separated from OpJiiccepJialus owing to its 



