52 MALDONADO. [CHAP. ni. 



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 gradual \y-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 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 uubbles 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 

 species 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 



