BY J. BURTON CLELAND. 269 



the neck. This area would seem to be far too small, considei iriir 

 the bulk of the animal, to assist materially in coordinating the 

 body-heat to a constant mean temperature in the presence of 

 great solar heat and muscular exercise; and hence the keeping 

 down of the temperature, under these conditions, must depend 

 chiefly on invisible perspiration and vaso-motor processes. This 

 small amount of visible perspiration, by conserving the animal's 

 water-supply, is doubtless of great advantage to a creature 

 inhabiting arid regions. 



It may be of interest also to bear in mind, in connection with 

 this reptilian temperature-trait, the fact of the oval shape of the 

 red corpuscles of camels, which, though not nuleated, thus far 

 also resemble those of reptiles and birds. One cannot see any 

 actual relation between these two reptilian traits in camels. The 

 camel, being a ruminant, has presumably evolved along with 

 other ruminants, and, in consequence, its ancestry must be sup- 

 posed at one time to have possessed round corpuscles like other 

 ruminants, and so on, dating back to marsupial or premarsupial 

 times. The appearance, then, of an oval corpuscle would seem to 

 indicate either an atavistic (or rather reversionary) phenomenon, 

 or a new evolutionary departure suiting the structures of the 

 animal. Recently the view has been propounded that the 

 appearance of one reversionary character, or of some new departure, 

 may be associated with others not apparently related to it; and 

 that, by artificial selection, an attempt to breed a stock contain- 

 ing the one will lead to the production of a race in which both 

 are stable. Can the appearance of the one trait, being of use to the 

 animal in some way, by natural selection have rendered the other 

 permanent also? On the other hand, what conceivable advantages 

 can there be to camels to possess either oval red cells, or a tem- 

 perature varying considerably with their external surroundings 1 

 Perhaps the soundest view to take will be to consider the oval 

 red corpuscles as having arisen by a pure mutation, of no par- 

 ticular economic value even physically, and the oscillations of 

 temperature as the result of a successful attempt to conserve 

 water. 



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