210 



KNOWLEDGE. 



[September 2, 1895. 



the ditches of the South Carolina rice-fields ; but another 

 specimen was caught in a well in Lebanon County, 

 Tennessee, in the year 1854. They appear to have taken 

 to a partially subterranean life comparalively recently, and 

 therefore retain their eyes and dark coloration. 



Although these cave-fish are clearly allies to the 

 cyprinodonts, there is no evidence to show that they are 

 directly descended from any member of that family. Such 

 a descent is, however, indicated by a very remarkable 

 family of fishes known as the OiiJii/liifltr, which are near 

 relatives of the cod tribe. With the single exception of 

 the cave-fish of the caves of Cuba [Lucit'w/<i dentata). 



FlO. 2.— Cuban Cave-Fish. 



all the members of the family are marine forms, some 

 inhabiting shallow water, while others are found only at 

 great depths. Now the Cuban blind fish, in which the 

 eyes are either totally wanting or rudimentary, is a very 

 close ally of a marine form named liratula, in which the 

 eyes are fully developed, and has evidently been specially 

 modified from the former for a subterranean existence. 

 The barbels, which are present in the marine fish, are 

 replaced in the cave form by minute tubercles. This, 

 however, is not the only point connected with this curious 

 family, as there are two species, belonging to as many 

 genera {Ti/plihinus and Ajihi/nnus), founl at great depths in 

 the southern oceans, which are also completely blind, and 

 apparently have no phosphorescent organs. And it would 

 appear from these examples that the fish of this family 

 have some special disposition towards a life of darkness. 



The only other fish that can be said to belong to the 

 cave-fauna is a member of the great freshwater family of 

 cat-fishes {SiluridcB), and has been named by Prof. Cope 

 (rronias niiii-il(ilirif>. This fish, which attains a length of 

 about ten inches, is closely allied to an ordinary freshwater 

 American form, and occurs in the Conestoga river in 

 Lancaster County, Pennsylvania, where it is stated to be 

 occasionally taken by the fishermen, and is believed to 

 issue from a subterranean stream said to traverse the 

 limestone of that district, and to discharge into the 

 Conestoga river. Although blind, this fish has a rudimental 

 eye, and is therefore in process of modification for a com- 

 pletely subterranean life. 



To refer in detail to the invertebrate inhabitants of caves 

 would far exceed our allotted limits, and only a few words 

 can be said on this part of the subject. Among the most 

 interesting are the blind cray-fish, in the ordinary form of 

 which (('iiiiihiirux) the eyes are rudimental in the adult, 

 but larger in the young, thus affording conclusive evidence 

 of their descent from forms fully endowed with vision. 

 Prof. Cope has, however, described one crayfish from 

 the Wyandotte cave in which the eyes are completely 

 wanting. Among the insects, there is a totally blind 

 beetle [Annjihthdmus) belonging to the family of Carabid<r, 

 or tiger-beetles, from the American caves ; while those of 

 France and Ireland have yielded a blind and colourless 

 spring-tail (Lipiira). Wingless grasshoppers are abundant, 

 but these, at least generally, can see. Centipedes and 

 spiders are also common, one of the former from the 



Mammoth cave being totally blind, while others retain 

 their eyes. In the European species of cave-spiders 

 {Parrhomd) the eyes are excessively minute, and tend to 

 become obsolete ; but it is noteworthy that these creatures 

 belong to a genus in which the eyes are small even in the 

 open-air kinds. 



It is thus apparent that all cave-animals are descended 

 from allied forms living in the outer world, and that in 

 many cases they belong to families which appear specially 

 adapted for modification to a subterranean existence. 



One of the most interesting discoveries is the close 

 alliance between creatures inhabiting caves widely 

 remote from one another. Writing of the animals 

 of the Mitchelstown cave, Mr. G. H. Carpenter 

 observes that the springtail "is hardly to be 

 separated from a species found in the caves of 

 Carniola, and the Sinella (another blind and 

 bleached insect) is almost identical with one in- 

 habiting ihe caves of North America ; while the 

 spider is apparently the same as a cave-dweller from 

 the Mediterranean district of Southern France, 

 which probably occurs in the North American 

 caverns also. . . . Any possible geographical 

 connection which would permit the migration of 

 subterranean animals between Southern Europe or Ireland, 

 or between Ireland and North America, seems altogether 

 out of the question within any period during which the 

 fauna can have been specifically identical with that of the 

 present day. The only conclusion is that from ancestors, 

 presumably of the same genus, which took to an under- 

 ground life in such widely-separated localities, the similar 

 conditions of the caves have evolved descendants so similar 

 that when compared they cannot, or can hardly be speci- 

 fically distinguished from each other." 



Should these identifications be confirmed, it will be 

 evident that the same, or closely allied species, have 

 originated independently in different caves, and although 

 the author cited is of opinion that this phenomenon may 

 only hold good with regard to cave-animals, we are 

 inclined to think that it may be found also to exist in the 

 outer world, since it has been suggested that the horses 

 {F.ijui) have originated independently in the Old and New 

 Worlds from different ancestral stocks. 



HELIUM, TOGETHER WITH A FEW NOTES ON 

 ARGON. 



By George McGowan, Ph.D. 



ALTHOUGH only five months have elapsed since 

 Prof. Rimsay announced his discovery of terres- 

 trial helium to the Chemical Society at the 

 anniversary meeting of thelatter on March 27tli, 

 the large number of letters and papers — specula- 

 tive and otherwise — which have since been contributed to 

 scientific journals and magazines, either upon helium alune, 

 or upon helium and argon together, shows what wide- 

 spread interest it has awakened. The July number of the 

 Jouytiirl (if the Cliemicil Societi/ contains a further paper 

 upon " Helium, a constituent of certain Minerals," by Prof. 

 Ramsay, Dr. Collie, and Mr. Travers, which gives the 

 results of their work upon the new gis up to date ; it 

 seems, therefore, a fitting opportunity to present a short 

 sketch of the subject to the readers of Knowledge. 



Nearly thirty years have passed since the spectrum of 

 the solar chromosphere and prominences was discovered to 

 consist of the lines of hydrogen, and of a bright line in the 

 yellow, since known as D^. But, until the other day, 



