Niphargus Kochianus and N. subterraneas. 275 



species of small blind Crustacea, both Isopoda and Ampliipoda, 

 are known to inhabit wells and caves in many parts of the 

 world. Chilton has described no less than six from Nevv 

 Zealand, Packard and Cope several from North American 

 cave-waters, while those of France, Switzerland, and el-^e- 

 where in Europe have occupied the attention of numerous 

 zoolo^'ists. 



Niphargus and the nearly related Crangonyx have been 

 referred by some early authors to Gammarus as the ancestral 

 type, of which the most familiar species is Oammarus piih.r, 

 the common "• freshwater shrimp/^ But careful examination 

 of the respective generic characters has resulted in a general 

 consensus of opinion that these blind subterranean genera 

 have originated from some extinct freshwater ancestor witli 

 eyes, from which Gammarus has also descended, so that they 

 are not merely modified and degenerate Gammarids. And 

 this view has certainly been strengtliened by the discovery 

 of an eyed form of Crangonyx (^gracilis, Smith) in Lake 

 Superior, while others have been tound in surface-streams in 

 America, and in Tasmania a nearly related form, also with 

 eyes, has been noticed. J\[ore than one species of Niphargus 

 with perfect eyes are known too from the Caspian and Black 

 Seas. It seems, therefore, extremely probable that the blind 

 subterranean Crustacea descend from widely distributed 

 freshwater eyed forms, some of which are still extant. In 

 English well^, especially in the southern countias, several 

 blind forms of Niphargus and one Crangonyx are known to 

 occur. Only recently the writer obtained specimens of 

 N. subterraneus, Leacli, and probably N. fontanus {puteanus, 

 Koch), from deep wells near Lynsted, Kent. But in Ireland, 

 so far, only N. Kochianus^ Bate, from a well near Dublin, 

 has been recorded. This species has never been hitherto 

 found in an open sheet of water. Two other blind species 

 have, however, been found in freshwater lakes : namely, 

 N. orcinus, discovered in 1868 by Gustav Joseph in the Luke 

 of Zirknitz, where he reports them to be plentiful and that 

 they come to the suiface in fine weather after sunset. They 

 frequent the brooks flowing from the hill-grottoes of Carniola, 

 whence he supposes them to have descended into the lake. 

 Another, N. suhterraneus, var. Forellij found by Prof. Forel 

 in tlie deep waters of Lake Leman, has been carefully 

 described by Alois Humbert. It was subsequently discovered 

 in hve otiier Swiss lakes, and both Forel and Humbert 

 eventually came to the conclusion tliat they found their way 

 thither from subterranean sources, and got acclimatized to 

 their nevv habitat. The phenomenon of hereditary blindness 



