1846.] Darwin's Voyage, of a JVaturalist. 267 



reared in the provinces near the Plata show their less civilized 

 origin, in being fiercer than common cattle, and in the cow easily 

 deserting her first calf, if visited too often or molested. It is a 

 singular fact, that an almost similar structure to the abnormal* 

 one of the niata breed characterizes, as I am informed by Dr. Fal- 

 coner, that great extinct ruminant of India, the Sivatherium. 

 The breed is very true ; and a niata bull and cow invariably 

 produce niata calves. A niata bull with a common cow, or the 

 reverse cross, produces offspring having an intermediate character, 

 but with the niata characters strongly displayed: according to 

 Senor Muniz, there is the clearest evidence, contrary to the com- 

 mon belief of agriculturists in analogous cases, that the niata 

 cow when crossed with a common bull, transmits her peculiarities 

 more strongly than the niata bull when crossed w^ith a common 

 cow. When the pasture is tolerably long, the niata cattle feed 

 with the tongue and palate as well as common cattle; but during 

 the great droughts, when so many animals perish, the niata breed 

 is under a great disadvantage, and would be exterminated if not 

 attended to; for the common cattle, like horses, are able just to 

 keep alive by browsing with their lips on twigs of trees and 

 reeds; this the niatas cannot so well do, as their lips do not join, 

 and hence they are found to perish before the common cattle. 

 This strikes me as a good illustration of how little we are able to 

 judge from the ordinary habits of life, on what circumstances, oc- 

 curring only at long intervals, the rarity or extinction of a species 

 may be determined. 



Farmers of this and the New England States have complained 

 of the Canada thistle, and have felt that it is so much of a nui- 

 sance as to call for legislative enactments for its extirpation. Let 

 us see what kind of thistles Mr. Darwin saw on the fertile para- 

 pas near Mercedes on the Rio Negro: — 



2\st. — Started at sunrise, and rode slowly during the whole 

 day. The geological nature of this part of the province was 

 different from the rest, and closely resembled that of the Pampas. 

 In consequence, there were immense beds of the thistle, as well 

 as of the cardoon: the whole country, indeed, may be called one 

 great bed of these plants. The two sorts grow separately, each 

 plant is company with its own kind. The cardoon is as high as 

 a horse's back, but the Pampas thistle is often higher than the 

 crown of the rider's head. To leave the road for a yard is out of 



'A nearly similar abnormal, but I do not know whether hereditary, struc- 

 ture has been observed in the carp, and likewise in the crocodile of the 

 Ganges : Histoire des Anomalies, par M. Isid. Geoffrey St. Hilaire, torn, i., 



p. 244. 



