52 MALDONADO. [chap. hi. 



common, cannot be a very serious evil ; yet it appears strange 

 that any animal should possess an organ frequently subject to be 

 injured. Lamarck 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 

 d)ubt 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 with- 

 out 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. 



Birds of many kinds are extremely abundant on the undulat- 

 ing grassy plains around Maldonado. There are several species 

 of a family allied in structure and manners to our Starling : one 

 of these (Molothrus niger) is remarkable from its habits. Seve- 

 ral may often be seen standing together on the back of a cow or 

 horse ; and while perched on a hedge, pluming themselves in the 

 sun, they sometimes attempt to sing, or rather to hiss ; the noise 

 being very peculiar, resembling that of bubbles of air passing 

 rapidly from a small orifice under water, so as to produce an 

 acute sound. According to Azara, this bird, like the cuckoo, 

 deposits its eggs in other birds' nests. I was several times told 

 by the country people, that there certainly is some bird having 

 this habit ; and my assistant in collecting, who is a very accurate 

 person, found a nest of the sparrow of this country (Zonotrichia 

 matutina), with one egg in it larger than the others, and of a 

 different colour and shape. In North America there is another 

 tpecies of Molothrus (M. pecoris), which has a similar cuckoo- 

 like habit, and which is most closely allied in every respect to 

 the species from the Plata, even in such trifling peculiarities as 



* Philosoph. Zoolog., torn, i. p. 249 



