Seite - 150 - in The Origin of Species

ISO ORIGIN OF SPECIES than the mole; and I was assured by a Spaniard, who had often caught them, that they were frequently blind. One which I kept alive was certainly in this condition, the cause, as appeared on dissection, having been inflammation of the nictitating membrane. As frequent inflammations of the eyes must be injurious to any animal, and as eyes are certainly not necessary to animals having subterranean habits, a re- duction in their size, with the adhesion of the eyelids and growth of fur over them, might in such case be an advan- tage; and if so, natural selection would aid the effects of disuse. It is well known that several animals, belonging to the most different classes, which inhabit the caves of Carniola and of Kentucky, are blind. In some of the crabs the foot- stalk for the eye remains, though the eye is gone;—the stand for the telescope is there, though the telescope with its glasses has been lost. As it is difficult to imagine that eyes, though useless, could be in any way injurious to ani- mals living in darkness, their loss may be attributed to dis- use. In one of the blind animals, namely, the cave-rat (Neotoma), two of which were captured by Professor Silli- raan at above half a mile distance from the mouth of the cave, and therefore not in the profoundest depths, the eyes were lustrous and of large size ; and these animals, as I am informed by Professor Silliman, after having been exposed for about a month to a graduated light, acquired a dim per- ception of objects. It is difficult to imagine conditions of life more similar than deep limestone caverns under a nearly similar climate; so that, in accordance with the old view of the blind ani- mals having been separately created for the American and European caverns, very close similarity in their organisation and affinities might have been expected. This is certainly not the case if we look at the two whole faunas; and with respect to the insects alone, Schiodte has remarked, "We are accordingly prevented from considering the entire phenome- non in any other light than something purely local, and the similarity which is exhibited in a few forms between the Mammoth cave (in Kentucky) and the caves in Carniola, otherwise than as a very plain expression of that analogy