Ni|)hargus Koclii:inus and N. subterraneus. 275 



species of small blind Crustacea, both Tsopoda and Aiiipliipoda, 

 aio known to inhabit wells and caves in many parts of tlic 

 world. Chilton has described no less than six from New 

 Zealand, Packard and Cope several from North American 

 cave-waters, while those of France, SwitZ'Tland, and el-*e- 

 wherc in Europe have occupied the attention of numerous 

 zoolop^ists. 



^{phunjus and the nearly related Cnmgonyx have b.'en 

 referred by some early authors to Gam/narun as the ancestral 

 type, of which the most familiar species is Giimmarns puhXy 

 the common " freshwater shrimp." But careful examination 

 of the respective generic cliaracters has resulted in a general 

 consensus of opinion that these blind subterranean genera 

 have originated from some extinct freshwater ancestor with 

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

 are not merely modified and degenerate Gammarids. And 

 this view has certainly been strengthened 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. More than one species of Niphnrgas 

 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 wells, especially in the southern counties, several 

 blind forms of Niphargus and one Crangonyx are known to 

 occur. Only recently the writer obtained specimens of 

 N. suhterraneuSj Leach, and probably N. fontamis {puteanus, 

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

 so far, only N. Kuchianuft, 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 18G8 by Gustav Joseph in the Lake 

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

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

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

 whence he supjwses them to have descended into the lake. 

 Another, i\'. subterraneus, var. Forelli, found by Prof. Ford 

 in the deep waters of Lake Leman, has been carefully 

 described by Alois Humbert. It was subsequently discovered 

 in live other ISwiris lakes, and both Eorel and Humbert 

 eventually came to the conclusion that they found their way 

 thither trom subterranean sources, and got acclimatized to 

 their new habitat. The phenomenon of hereditary bliudness 



