September 2, 1895.] 



KNOWLEDGE 



209 



pleasure than is that of the inhabitants of the deep sea. 

 Possibly, however, there may be other compensating 

 advantages unknown to us ; and, in any case, they lead a 

 life of peace unmolested by the various carnivorous tyrants 

 of the outer world. It is, however, very noteworthy that 

 there is one blind fish inhabiting the ocean at great depths, 

 and that a member of the same family is also found in the 

 caves of Cuba ; and this instance seems to indicate that 

 certain families of fishes are better suited than others for 

 taking to a subterranean existence. 



Caves or subterranean channels containing the typical 

 blind fauna are met with in many parts, apparently in- 

 variably in limestone rocks, and mostly in those belonging 

 to the Carboniferous epoch ; the latter, from their massive- 

 ness, being especially adapted for the formation of such 

 chambers by the action of water. Needless to say, the 

 formation of a cavern of any size in solid limestone rock 

 is a process involving an enormous length of time for it^ 

 accomplishment, and it is therefore essential that the rock 

 should be of very considerable geological age. Indeed, it is 

 believed that the formation of the celebrated Mammoth 

 cave was commenced at a comparatively early date in the 

 Secondary era, although it was not completed till the 

 Pleistocene. The reader must not, however, be led to 

 suppose that cave-animals belong to an older epoch than 

 those of the outside world, as it is probable that many of 

 them have not taken to their present mode of existence 

 since the later Pliocene or early Pleistocene period. 



Caves of sufficient dimensions to have developed a special 

 fauna of their own are met w.th in so many parts of the 

 world, that it would be tedious to give a 

 list even of those which are most generally 

 known. Among those that have attained 

 the widest degree of celebrity is the 

 Mammoth cave, situated in a hill of lime- 

 stone in Edmonston County, a little to the 

 south- west of the centre of Kentucky. This 

 enormous cave is adorned with the most 

 beautiful stalaotitic and other deposits, 

 which, when lit by the magnesium or the 

 electric light, form an enchanting sight. 



Another well-known American example 

 is the Wyandotte cave, traversing the Carboniferous lime- 

 stone of Crawford County, in south-western Indiana. Of 

 this cave. Prof. Cope wrote in 1872 that he was not aware 

 whether its length had ever been accurately determined, 

 " but the proprietors say that they have explored its galleries 

 for twenty-two miles, and it is probable that its extent is 

 equal to that of the Mammoth cave. Numerous galleries 

 which diverge from its known courses in all directions 

 have been lelt unexplored.' The fact that the blind cave- 

 fish appears to occur in all the subterranean waters flowing 

 through the great Carboniferous limestone region of the 

 central districts of the United States, suggests that the 

 Mammoth and the Wyandotte caves are in communication. 

 Almost equally celebrated are certain caves in the island of 

 Cuba, which are also traversed by subterranean streams. 

 In Europe, perhaps the most interesting cave is that of 

 Adelsberg in Carniola, as being, together with certain other 

 caves in Carinthia and Dalmatia, the sole habitat of that 

 strange creature, the olm or proteus,so graphically described 

 many years ago by Sir Humphry Davy. Although the 

 Carinthian and Dalmatian forms of this creature diiler 

 slightly from the Carniolan type, there can be little doubt 

 that the subterranean waters of all thethree countries are, or 

 were at a comparatively recent date, in free communication. 

 Several caves with the blind fauna are met with m Western 

 Europe, some of the most notable being those in various 

 parts of the south of France ; but the only one in the 



British Islands is Mitchelstown cave, near Fermoy, in 

 Ireland, which is excavated in the Carboniferous limestone. 

 The animal of the highest zoological position occurring 

 among the true cave-fauna is the aforesaid olm, which is 

 the sole representative of the genus Proteus, and is allied 

 to the ordinary salamanders and newts. The olm is a 

 somewhat eel-like creature, measuring about eleven inches 

 in length, and with a uniformly flesh-coloured skin, sava 

 that the branching external gilh are brilliant scarlet. The 

 limbs are very short and weak, the front pair being provided 

 with three and the hinder with two toes, and the eyes are 

 completely hidden. Now it is a most remarkable fact that 

 the only other salamander referred to the same family 

 (Prott'id(p) as the olm is a single North American speciej 

 with well-developed eyes, four toes to each foot and a dark 

 brown skin, which constitutes the genus Nfctitnis ; and 

 from this it may be inferred that the ancestral type of the 

 two genera formerly inhabited the northern hemisphere, 

 and that while its transatlantic descendant has preserved 

 the primitive number of toes and adhered to an ordinary 

 mode of life, the European species has become more 

 specialized in regard to its limbs, and has taken to a 

 completely subterranean existence. According to Sir 

 Humphry Davy, the olm only makes its appearance in 

 the Adelsberg grotto when the waters rise to an unusual 

 height, remaining at other periods in the streams flowing 

 beneath its floor. 



The only other vertebrate animals belonging to the true 

 cave-fauna are fish of several species. By far the most 

 celebrated among these is the well-known blind-flsh 



Fig. 1.— The Blind-lush. 



fAmhhjojiiis spdccai, which has been taken in both the 

 Mammoth and the Wyandotte caves, as well as in the 



I intervening subterranean waters. This fish is the typical 

 representative of a small family allied to the cyprinodonts, 

 which are themselves relatives of the carps. It is quite 

 destitute of external eyes, and its body is completely 

 colourless; but its sense of hearing is extritordmarily 

 developed. In the typical form this fish has a small pair 



i of pelvic fins, but in some examples (which have been 



I referred to a distinct gemis under the name of Ti/phlichthys) 

 these are wanting. The maximum length is five inches. 

 Prof. Cope writes that if these fish "be not alarmed, 

 they come to the surface to feed, and swim in full sight 

 hke white aquatic ghosts. They are then easily taken by 

 the hand or net, if perfect silence is observed, for they are 

 unconscious of the presence of an enemy except through 

 the medium of hearing. This sense is, however, evidently 



I very acute, for at any noise they turn suddenly downward, 

 and hide beneath stones, etc., at the bottom. They must 

 take much of their food near the surface, as the life of the 

 depths is apparently very sparse." 



The only other genus in the family is known as 



: Choloiiaster, difi'ering from the last in the retention of 

 small" external eyes, and likewise in the skin being 

 coloured. Pelvic fins are absent, and the front of the 

 head is provided with two horn-like appendages. These 

 small fish were first known from three examples taken in 



