CEUSTACEA OF NEW ZEALAND. 259 



it still preserves the distinguisliing marks of Gammarus and shows no approach in 

 structure to ]Sij)liargtis. Professor Forel points out that there mvist be means of com- 

 munication — not necessarily permanent — between the subterranean waters and the deep 

 waters of the lakes and also between the subterranean waters of different localities, thus 

 fully confirming what I had already -wTitten above pn p. 258 before I had read 

 Professor Porel's remarks on the subject. 



VIII. The Special Characteristics of the Subterranean Fauna. 



The special conditions of cave- and well-life and the peculiarities of the subterranean 

 fauna have been discussed more or less elaborately by many authors, and a complete 

 dissertation on the subject would require a volume to itself. All that can be done here 

 is to mention a few j)oints upon which information is supplied by the six subterranean 

 Crustacea described in this paper. The subject has been fully discussed by Schiodte, 

 Joseph, and Packard; and Forel has considered the conditions of life in the deep waters 

 of the Swiss Lakes, the fauna of which presents many analogies to that of the under- 

 ground waters. 



Colour. 



The effect of the absence of light on the colour of all animals living in caves and 

 in underground waters seems to be very uniform, all such permanent residents being 

 bleached and colourless. Speaking of the inhabitants of caves, Packard says : — 

 " As regards change of colour, we do not recall an exception to the general law, that 

 all cave-animals are either colourless or nearly white, or, as in the case of Arachnida and 

 insects, much paler than their out-of-door relatives " [83, p. 117]. 



The same statement might be made concerning the inhabitants of underground waters, 

 different authors speaking of them as " colourless," "snow-white," " translucent," &c. The 

 Crustacea are usually more or less translucent, vitreous, and pellucid, though by no means 

 so much so as pelagic members of the same group. The six species dealt with in this 

 paper may be described as white or colourless, more or less translucent. I have sometimes 

 noticed a slight pink or rosy tint on the body of CaUlopins subterraneus, which is most 

 apparent in female specimens bearing eggs, and then appears to arise chiefly from the yolk 

 of the eggs themselves ; the " liver "-tubes of Cruregens fonkmus, which can easily be 

 seen through the transparent integument, are of a very pale yellow colour, and the tip 

 of the dactylos of the first pair of appendages of the peraeou (gnathopoda) is of a very 

 distinct but light bro^\Ti. 



The subterninean worm Phreodrilus subterraneus, Beddard, is stated by Mr. Smith 

 (quoted by Beddard [8, \}. 273]) to be " fleshy red " during life. This is chiefly due to 

 the red colour of the fluid in the various vessels of the vascular system, the integument 

 and the greater part of the body being colourless ; this was plainly seen in a very fine 

 specimen that Mr. Smith kindly sent alive to me in September 1892. 



Professor S. I. Smith has pointed out that the deep-sea Crustacea present a marked 

 contrast to cave Crustacea in colour. In a general account of the Crustacea of the 



SECOND series. — ZOOLOGY, VOL. VI. 31 



