3^ The Irish Naturalist, 



the former, the appendages of Z. Wrightii are not so short and stumpy 

 as those of the latter, which, however, our species resembles much in 

 general structure, and in the absence of anal spines. It seems probable 

 that it may be really an offshoot of L. fimetaria, modified for cave-life, 

 the lengthening of antennae being a common occurrence in subterranean 

 insects. These considerations have induced me to give the insect a new 

 name, and none could be more suitable than that of the naturalist whose 

 earliest paper announced its discovery, and who has since done so much 

 to advance the knowledge of Irish Natural History. 



Reviewing these animals, we notice that (except the mite) 

 they all present the characters of true troglodytes. All 

 are more or less bleached, the two insects being perfectly 

 white. The two insects are totally blind (the mite, of course, 

 cannot be reckoned, as it belongs to a blind family), and the 

 spider is clearly in process of becoming so. The peculiar 

 modifications which cave animals have undergone have been 

 variously explained, and have been much used by recent 

 writers in discussions upon the factors of evolution. The 

 bleaching and loss of eye-sight which these creatures exhibit 

 are by some attributed solely to their life in total darkness, b}^ 

 others to the action of natural selection with regard to some 

 portions of their organization and its necessary cessation 

 (panmixia) with regard to others, in the new surroundings. 



No naturalist doubts that these cave-dwellers are the modi- 

 fied descendants of inhabitants of the upper air, which were 

 provided with eyes, and coloured after the usual manner of 

 their genus. There can be no doubt that the production of 

 pigment is largely dependent upon the presence of light, and 

 it seems very likely that a life in darkness is alone sufficient 

 to account for the bleaching characteristic of cave-dwellers. 

 Instances are given by Professor Packard of individuals belong- 

 ing to the open-air fauna being quite bleached when found in 

 caves, the loss of colour having here occurred during the life- 

 time of the individual. On the other hand, colour must be 

 absolutely useless to dwellers in total darkness, to conceal 

 them either from enemies or prey, and would therefore tend to 

 disappear through the cessation of selection of individuals 

 coloured in any particular way. Similarly, the loss of eyes 

 may be attributed either directly to disuse through a life in 

 darkness, or to the cessation of selection with regard to those 

 organs, since they can be no longer of use to their possessors. 

 Professor Ray Lankester has suggested that animals with 



