52 MALDONADO. [omar. IIL. 
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-aeguired 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 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 
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., tom. i. p. 242 
