108 HEADWATERS OF THE PARAGUAY 



The whitetail deer — using the word to designate a 

 group of deer which can either be called a subgenus 

 with many species, or a widely spread species diverging 

 into many varieties — is the only North American species 

 which has spread down into and has outlying repre- 

 sentatives in South America. It has been contended 

 that the species has spread from South America north- 

 ward. I do not think so ; and the specimen thus ob- 

 tained ftirnished a probable refutation of the theory. 

 It was a buck, and had just shed its small antlers. The 

 antlers are, therefore, shed at the same time as in the 

 north, and it appears that they are grown at the same 

 time as in the north. Yet this variety now dwells in 

 the tropics south of the equator, where the spring, and 

 the breeding season for most birds, comes at the time 

 of the northern fall in September, October, and Novem- 

 ber. That the deer is an intrusive immigrant, and that 

 it has not yet been in South America long enough to 

 change its mating season in accordance with the climate, 

 as the birds — geologically doubtless very old residents 

 — have changed their breeding season, is rendered prob- 

 able by the fact that it conforms so exactly in the time 

 of its antler growth to the universal rule which obtains 

 in the great arctogeal realm, where deer of many species 

 abound, and where the fossil forms show that they have 

 long existed. The marsh-deer, which has diverged much 

 farther from the northern type than this bush-deer (its 

 horns show a hkeness to those of a blacktail) often 

 keeps its antlers until June or July, although it begins 

 to grow them again in August ; however, too much 

 stress must not be laid on this fact, inasmuch as the 

 wapiti and the cow caribou both keep their antlers until 

 spring. The specialization of the marsh-deer, by the 

 way, is further shown in its hoofs, which, thanks to its 



