25(5 DE. C. CHILTON ON THE SUBTEEEANEAN 



or from caves and wells in England {C.subterraneus), Italy {C. imngens). North America 

 {C. gracilis, C. viireus, &c.), Kamtschatka {C. Evmanni), New Zealand (C. compactus), 

 and a form more or less closely allied still inhabits the fresh waters of Tasmania ; 

 Callioplus subterraneus appears to have its nearest ally in Pherusa ccsrulea, found in a 

 stream ou the top of mountains 3000 feet high in Otago, New Zealand, while another 

 species {CalUopius fluviatilis), which perhaps belongs to the same genus, is very abundant 

 in the freshwater streams of the South Island of New Zealand ; no freshwater form at 

 all approaching Cruregens is as yet known ; besides the two subterranean species, the 

 only other known ^T^eciQs, oi Phreatoicus is found on the top of the Mt. Kosciusko Plateau 

 in Australia, living in pools and streams. 



It will thus be seen that there is no difficulty in supposing that the subterranean fauna 

 of New Zealand has been derived directly from a freshwater fauna, and when we consider 

 the affinities of the general fauna of the North-American caves as given by Packard [83], 

 or of the various Euroi^ean caves, there can no longer be any doubt that the cave- and 

 well-fauna has been derived from the surface-fauna of the neiohbourhood. 



While this conclusion thus appears to be well founded, it by no means foUows that the 

 subterranean fauna is necessarily derived from the freshwater fauna at present inhabiting 

 the surface-streams and lakes ; indeed there are several facts which seem to show that 

 some species at any rate are derived from a more ancient surface-fauna. Thus, while 

 the subterranean species Asellus cavaticus may perhaps be the direct descendant of 

 the surface-species A. aquaticus, there is no doubt that Niphargus is not a mere 

 modified form of any of the surface-inhabiting Gammari at present found in Europe. 

 Wrze^niowski has clearly pointed out that experiments like those made by Eries and 

 observations on pale forms of Gammarus found in mines, &c., like the one described by 

 Schneider, do not bear on the question, for the specimens approach Niphargus only in 

 the pale body and in the partial loss of the eyes while still retaining the general build 

 and characteristic mouth-parts, &c., of Gammarus. As to the actual origin of Gammarus 

 and Niphargus we are, he says, quite in the dark ; but he is of opinion that neither is 

 derived from the other, but both from a common ancestor. Humbert had previously 

 come to much the same conclusion and is of opinion that Nlpjhargus is an ancient 

 genus derived from a form now extinct. 



The Crayfish inhabiting the caves of North America also appear to be more ancient 

 than those at pi'esent found in the surface-water of the neighbourhood. Speaking of 

 Cambarus pelluciihis. Professor Eaxon says it " is a very aberrant species, with no very 

 closely related form outside the cave. The simple form of the male appendages, and the 

 combination of characters belonging to different groups, seen in C. pellucidtis, indicate, 

 to my mind, that it is a very ancient form, which has been preserved in the seclusion 

 of the cave, whilst its nearest kin supcumbed in the sharper struggle incident to life 

 outside, or were replaced by modified descendants evolved to meet the changeable con- 

 ditions which obtain witliout the caverns " [37, p. •^"1]. 



This view is, he says, confirmed by the fact that the same form, C. pellucidus, is found 

 in caves on both sides of that ancient river, the Ohio, and by the discovery by Gustav 

 Joseph of a species of Cambarus in the caves of Carniola in Southern Austria. As the 



