On some Freshwater Amphipods. 227 



XXXVII. — On some Freshwater Amphipods : The Reduction 

 of the Eye in a new Oammarid from Ireland. By Prof. Dr. 

 Fr. Vejdovsky*. 



[Plates XI. & XII.] 



The paper by W. F. de Vismes Kane (23) on the Amphipods 

 of the Irish lake, Lough Mask, is wortliy of attention in 

 many ways. It records that tlie author collected there about 

 130 specimens of Niphargus Kochianus, among which there 

 were three " which had well-developed pigmentation and a 

 fourth which showed a cloudy shading in the optic region." 

 As I had already stated (22) that in " N. Kochianus'" rudi- 

 ments of eyes without pigment are present, I was obliged to 

 devote special attention to the work of de Vismes Kane, 

 according to which pigment was still actually to be found in 

 certain individuals. 



Mr. de Vismes Kane, with the greatest kindness, placed at 

 my disposal, for purposes of investigation, a portion of his 

 collection of the above-mentioned Gammarids from Lough 

 Mask, including examples of the wholly blind Niphargus and 

 also the four individuals with the eye-flecks which had been 

 preserved in formol. This valuable material, for which I 

 here wish to thank Mr. de Vismes Kane, proved to be of 

 great importance for several reasons, viz. : — 



(1) Because it furnishes evidence as to the extent of the 

 first stage in the reduction of the compound eye ; 



(2) Because by reason of this degeneration it is possible to 

 explain the significance of the " pigment-veil " [Pigment- 

 schleier] already known in Crangonyx suhterraneus ; and 



(3) Because, lastly, it offers the possibility of deciding 

 the relationship of the freshwater shrimp [Flolikrebs] found 

 in the wells of Munich, usually alluded to as Niphargus 

 " Kochianus,'''' with the similarly designated species from 

 England and Ireland. 



I. On Bathyonyx^ gen. nov. 



In his paper de Vismes Kane refers all the Gammarids 

 found in Lough Mask to a single species, viz., Niphai-giis 

 Kochianus, Bate. I have been able to confirm this identifi- 

 cation with the exception of those four individuals with eye- 



* Translated by D. J. Scourfield from the ' Sitzungsbericlite der 

 luiniglichen bohinischen Gesellscliaft der Wissenschaften,' No. 28. 

 I'rair, 1005. 



