252 DE. C. CHILTON ON THE SUBTEEEANEAN 



Professor Eorel, in considering the origin of the blind Niphargus Forelii and Asellus 

 Forelii, comes to the conclusion that they have originated, not in the lakes themselves, but 

 in the underground waters, and he gives various interesting facts showing the commu- 

 nication that must exist between these waters and the deep waters of the lakes [40, 

 pp. 182-183 &c.]. The same thing is found in North America, for some of the blind 

 cave-species, Ccecidotcea stygia for example, are obtained from wells in various districts, 

 showing that they exist wddely spread in the underground waters, and not merely in the 

 caves themselves. It is possible that some of the species, perhaps Ccecidotcea stygia, may 

 have originated in the underground waters, and not actually in the caves, thus forming 

 an exact parallel to the case of Aselltts Forelii in the Swiss lakes. 



It wall not be necessary to bring forward any additional facts to show that there must 

 be abundant opportunities by which specimens of the freshwater fauna of any country 

 might be carried into the underground waters which almost everywhere exist, and thus 

 have a chance of giving rise to subterranean species. 



In the case of the Canterbury Plains, the subterranean waters have almost everywhere 

 sunk several feet further from the surface of the land during recent years, owing to a 

 succession of exceptionally dry seasons. Thus at Eyreton the level of the water has 

 sunk on an average about 10 or 12 feet ; Miss Young tells me that it has sunk also at 

 Winchester, and that the well there, from which subterranean Crustacea have been 

 obtained, has had to be deepened, and it will be seen from the following interesting 

 account, prej)ared by Mr. W. W. Smith, that the lowering of the water has been very 

 marked at Ashburton : — 



" Previous to the years 1890 and 1891 no lowering or discoloration of the subterranean 

 water was observed on the plains, at least there are no records of such existing. The 

 water in the pipe-wells and in the outflowing streams at the base of the terraces of the 

 Ashburton river, and also in the sui'face springs on the plains, remained constant at all 

 seasons and perfectly pure. As the drought increased, the water in the pipe-wells 

 lowered, and left them all, with one exception, dry. Near one house a large surface 

 spring rose in a small gully, and discharged a heavy flow of cool pure water. It began to 

 diminish in volume in October 1890, and by the December following it had ceased to 

 flow. The terrace springs, situated 25 feet lower, held out several months longer, and they 

 in turn gradually became dry. Half a mile below Ashburton a large strong-flowing 

 spring exists right in the river-bed ; it is distant about a quarter of a mUe from the 

 nearest terrace, and situated 12 feet below it. It flows out of a partially conglomerated 

 bed of small stones and clay, and unquestionably belongs to a lower stratum or stream 

 of water than those supplying the pipe-wells in the town. The water in this spring is 

 never affected in volume or colour by the flooding of the river, but retains its purity at 

 all seasons. The nearest terrace is 12 feet above it, and is composed chiefly of clay. It 

 is only a few feet above the stratum of water which supplies the wells in the town. 

 Before the drought several springs arose at the base of the terrace, none of which, nor 

 any of the surface-springs, have at present recommenced to flow. 



" I may mention that Mr. W. F. Dohnan, a practical well-sinker in business here, 

 informed me that there is no question about the water flowing between the various strata 



