CRUSTACEA OF NEW ZEALAND. 267 



It is, however, with regard to the effects of the disuse of organs that the cave and 

 subterranean fauna has been studied with the greatest interest, and here we closely 

 approach the controversy between the Neo-Darwinians and the Neo-Lamarckians. While 

 it would be utter presumption on the part of the writer to enter upon a discussion of this 

 question, it will be interesting to review a few of the opinions expressed by various 

 writers on the subject in so far as it is exemplified by the phenomena of subterranean 

 life. 



Darwin, in his ' Origin of Species ' [35, pp. 110-112], after pointing out that in the 

 case of the mole and similar burrowing animals natural selection will probably aid the 

 effects of disuse in producing blindness, refers to the blind inhabitants of caves, and 

 remarks : — " As it is diflicult to imagine that eyes, though useless, could be in any way 

 injurious to animals living in darkness, their total loss m^ay be attributed to disuse " 

 [35, p. 110]. 



Further on, after quoting Schiodte's observations as to animals, some of which are 

 adapted to the twilight and others to the perfect darkness of caves, he observes : — 

 •' By the time that an animal had reached, after numberless generations, the deepest 

 recesses, disuse will on this view have more or less perfectly obliterated its eyes, and 

 natui"al selection will often have effected other changes, such as in increase in the length 

 of the antennae or palpi, as a compensation for blindness " [35, p. 111]. 



That animals living in darkness do as a general rule gradually lose their eyes is now a 

 very familiar fact, and it no doubt appears at first sight simplest to explain this as an 

 example of the effects of disuse ; but there are numerous instances known of animals 

 living in darkness that yet possess more or less perfect eyes, and unless these can be 

 accounted for in some way they would appear to prove that the effect of darkness, per se, 

 does not necessai-ily produce degeneration of the eyes. Semper, in his ' Animal Life ' 

 [99, pp. 76-37], after giving a number of examples of the loss of eyesight apparently 

 through disuse, adds that " it would nevertheless be wholly false to assume that lack of 

 light must necessarily lead to total or partial blindness " [99, p. 81] ; he then 

 proceeds to give examples of animals living in darkness with more or less perfect eyes, 

 and on the contrary, of animals blind or half-blind, which yet " live in well-illuminated 

 situations, where the moderate intensity of the light would allow them the full use of 

 eyes." The examples given by Semper have been considered in detail by Packard [83, 

 pp. 130-132], who points out that some, at any rate, of the first group are " twiliiht 

 animals," living near the entrance of the caves as well as in the total darkness of the 

 innermost recesses, and that those animals which live in total darkness may perhaps cross 

 with those living near the entrance, and the eyes thus remain unimpaired. Other cases, 

 in which our knowledge is not so complete, may, he considers, perhaps be explained in 

 the same way ; and with regard to the second group, /. e. blind or half-blind animals livin" 

 in well-lighted situations, many may spend the greater part of their lives burrowing in 

 the mud or in dark places where eyes would be of little or no service to them ; in this 

 way he explains the blind Cymotlioa mentioned by Semper [99, p. S3] which he found in 

 the full light of day. 



"Wliilst some cases may perhaps be accounted for in this way, it does not seem tome that 



SECOND SERIES. — ZOOLOGY, VOL. VI. 35 



