44 'Charles Darwin. 



several yards, when they would run into the water 

 and dive, coming up to utter their singular bark. 

 Their tameness he ascribed to the fact that the 

 jaguar had almost disappeared from that locality, 

 and the Gauchos rarely hunted them. 



In the woods of Maldonado Darwin often heard 

 curious noises, arising apparently from the ground, 

 and resembling a bark or grunt. Investigation re- 

 sulted in finding a airious little subterranean and 

 nocturnal animal, the Tucutuco. Many of them 

 were blind or partly so, and we find the naturalist 

 speculating on the subject. " Lamarck," he says, 

 " would have been delighted with this fact had he 

 known it, when speculating (probably with more 

 truth than usual with him) on the gradually acquired 

 blindness of the Aspalax, a gnawer living under- 

 ground, and of the proteus, a reptile living in dark 

 caverns filled with water ; in both of which animals 

 the eye is in an almost rudimentary state, and is 

 covered by a tendinous membrane and skin. In the 

 common mole the eye is extraordinarily small, but 

 perfect, though many anatomists doubt whether it is 

 connected with the true optic nerve ; its vision must 

 certainly be imperfect, though probably useful to the 

 animal when it leaves its burrow. In the Tucutuco, 

 which I believe never comes to the surface of the 

 ground, the eye is rather larger, but often rendered 

 blind and useless, though without apparently causing 

 any inconvenience to the animal ; no doubt Lamarck 

 would have said that the tucutuco is now passing 

 into the state of the Aspalax and Proteus." 



We observe here that the young naturalist had 



