July 4, 1895] 



NATURE 



225 



phosphorescent. Judging from previous experience, the 

 presence of argon would have revealed itself after the 

 nitrogen had disappeared. It may therefore be concluded 

 that whether iron is permeable to argon at a red heat or 

 not, it docs not permanently retain the gas. It is not im- 

 probable that the condition of retention may be that the 

 iron is heated to fusion in an atmosphere of hydrogen, 

 hydrocarbons, argon, and helium, and that it is then 

 suddenly cooled. This I should imagine to be the case 

 if the iron were ejected from some stellar body at a high 

 temperature. I am, however, unaware whether any of 

 the lines of the argon spectrum have been identified in 

 the spectra of stars ; if not, it is probably because they 

 are masked by the spectra of hydrogen and carbon. 



W". Rams.w. 



SUBTERRANEAN FAUNAS. 



THE researches of geologists and engineers have re- 

 vealed the e.\istence of vast tracts of underground 

 waters, often associated with more or less e.\tensive 

 caves. The investigation of these underground waters 

 is interesting to naturalists, as it has led to the discovery 

 of a special subterranean fauna, different in different 

 regions, it is true, but characterised throughout by modi- 

 fications in certain definite directions. The study of 

 these modifications is a fascinating one, and the problem 

 of their evolution seems to be rendered comparatively 

 easy by the simplicity and limitations of the conditions 

 of life which obtain beneath the earth's surface ; for these 

 subterranean forms live in continual darkness, and are 

 exposed to a fairly uniform temperature at all times. It 

 is also, in many cases, possible to tell from what surface- 

 species an underground form has descended, and to 

 infer the age of the latter with a fair approach to 

 accuracy ; the nature of the changes undergone, and the 

 rate at which these modifications have taken place, can 

 thus be estimated in particular instances. 



It will be remembered that in Packard's well-known 

 memoir on the Cave Fauna of America, the peculiar 

 modifications of subterranean animals were interpreted 

 as lending strong support to the theory of the inherit- 

 ance of acquired characters. Recently, however, in a 

 careful and interesting memoir on the subterranean 

 Crustacea of New Zealand {Trims. Linn. Soc. London, 

 vol. vi., T894), Dr. Chilton considers the question from 

 the N'eo-Darwinian aspect ; and he adduces a number of 

 facts and arguments which greatly tend to reduce the 

 force of Packard's contentions. 



Dr. Chilton begins his memoir with a completed 

 account of the New Zealand subterranean Crustacea, 

 including a description of some new- species. The 

 underground crustacean fauna of New Zealand has a 

 more varied aspect than that of Europe or North 

 .\merica ; of the si.K species known, three arc -Xniphipods 

 and three Isopods, and these belong to as many as five 

 different genera, .\mong them Uivniiuirtis /nti;i/is is 

 interesting to us as being allied to the blind Nip/turgiis 

 of Europe. Crurcgcns Jonlnnus, an Isopod belonging to 

 the family .\nthurid;c, is curious in possessing only six 

 pairs of legs ; the seventh segment is small and without 

 appendages, as is the case also in young Isopods ; this 

 larval character is retained in Crurci^ens, probably owing 

 to an arrest in development on account of the scanty 

 supply of food. Two subterranean species of the genu's 

 Phreatoicits are described, P. typicus and P. assiini/is, 

 n. sp. ; a surface species, P. australis, lives on the 

 top of Mount Kosciusko in Australia. This genus is 

 peculiar, and the type of a new family of Isopods which 

 approaches the .-Xsellidiv in some respects, but differs in 

 the possession of a laterally compressed body and a long 

 six-jointed pleon. 



In addition to the description of these underground 



NO. 1340, VOL. 52] 



forms, the writer gives a ri.'nani' of our only too scanty 

 knowledge of the habits and conditions of life of subter- 

 ranean animals. He discusses also the question of the 

 origin of cave forms, and arrives at the conclusion that 

 the New Zealand subterranean Crustacea have clearly 

 been derived from a surface fauna, though the affinities 

 of one or two species seem to be rather with marine than 

 with known fresh-water forms. It is pointed out, how- 

 ever, that the cave fauna is not necessarily descended 

 from the present surface fauna of the country- ; Crangony.x 

 coiHpactus, for instance, has its nearest allies in Europe 

 and North .A.nierica, and the remarkable habitat of the 

 fresh-water species of Phreatoicus has already been 

 mentioned. 



Cave crustaceans, according to Packard, live " in a 

 sphere where there is little, if any, occasion for struggling 

 for existence between these organisms." Chilton, how- 

 ever, suggests that there is evidence for thinking that 

 Natural Selection has come into play in the evolution of 

 cave animals. He points out that the scanty supply of 

 food must inevitably lead to a keen struggle. Moreover, 

 Packard himself states that the Ccrcidotca and Crangony.x 

 of the North American caves are eaten by the blind cray- 

 fish, which in its turn is devoured by the blind fish 

 Aiiihlyopsis ; so that these animals must struggle with 

 their destroyers. To this end have probably been 

 developed the additional olfacton,' setiE, described by 

 Packard and others, to enable the pursued animals to 

 escape from their enemies. If there were no occasion 

 for struggling for existence, why should these additional 

 sense organs have been developed at all ? .\t first sight, 

 it certainly seems natural to attribute the degeneration 

 of the eyes, observed in underground forms, to disuse ; 

 and it is but a further step to assume that these new 

 characters, resulting from disuse and adaptation to new 

 conditions of life, were inherited by successive genera- 

 tions. But Chilton ingeniously remarks that, if the 

 modifications in the eyes of cave animals were the direct 

 inherited effect of the environment, we should expect to 

 find the lines of modification similar in all animals sub- 

 jected to the same conditions. This, however, is not the 

 case, as Packard's own investigations have shown. The 

 influences leading to degeneration act uniformly on all 

 individuals, but the modifications produced in the eyes 

 are various, and occur in different ways. In some cases 

 there is total atrophy of the optic lobes and optic nerves, 

 with or without the persistence in part of the pigment (or 

 retina) and the crystalline lens ; in others the optic lobes 

 and optic nerve persist, but there is total atrophy of the 

 rods and cones, retina, and facets ; while in extreme cases 

 there is total atrophy of the optic lobes and nerves, and 

 all the optic elements. These examples, showing a 

 development apparently capricious and varying in direc- 

 tion in animals all subjected to the same or similar 

 environment, point rather to the action of Natural Selec- 

 tion than to that of the direct inherited influence of the 

 conditions of life. 



In a more recent essay in the American Naturalist 

 (September i894\ Packard has restated his views on the 

 subject of the modifications of the eyes in subterranean 

 animals, and concludes his remarks with the following 

 words : "That while the heredity of acquired characters 

 was, in the beginning, the general rule, as soon as the 

 congcnitally blind preponderated, the heredity of con- 

 genital characters became the normal state of things." 

 In support of his view, Packard cites some statistics upon 

 the inter-marriage of deaf-mutes, which have been re- 

 cently furnished by Prof Graham Bell. It would appear 

 that, in .America at any rate, the segregation of deaf- 

 mutes within asylums has been followed by a striking 

 increase in intermarriages among them : so that, of the 

 deaf-mutes who marry at the present time, no less than 

 80 per cent, marrj' deaf-mutes. .A. marked increase in 

 the numljcr of the deaf-mute population has ensued, and 



