38 



Thompson in his " Art Anatomy of Amimals." He says 

 there the direction of hair is determined by two laws : — 



First, the necessity of offering the least possible 

 resistance to the air, and to grass, brushwood, and other 

 obstacles while the animal is inm otion. Secondly, the 

 necessity for running off the rain when the animal is at rest. 

 The first law, he says, gives a backward, and the second a 

 downward direction of the hair. He says, however, rather 

 significantly, " But these rules are much broken by local 

 requirements of more force." 



May we not reverse the whole of this statement and say 

 that the backward direction of the hair is produced by the 

 forces he mentions rather than produced b}' natural selection 

 for the purpose of adapting the body to the environments 

 referred to. In the case of a large and important surface 

 such as he alludes to the body and trunk of an animal like 

 the deer (which he tells us it is almost impossible to drag 

 along the ground when it is dead, against the set of the hair, 

 i.e., backwards, but very easy to drag forwards with the set 

 of the hair), some survival-value may be attached to the 

 direction of the hair. But to suppose that on closely similar 

 antelopes or carnivores it can effect the chances of survival 

 of the species that the hair should slope to the muzzle rather 

 than away from it, or that the presence of the whorls, 

 featherings, and crests to which I have referred as so 

 common, can have any conceivable effect upon the animal's 

 safety or even comfort, is not to be entertained. 



I have elsewhere maintained that on the nasal and 

 frontal regions of animals the set of the hair is determined 

 by the habits of the animals and the angle of incidence of the 

 wind, tropical rain, pressure of undergrowth, burrowing in 

 the ground, rooting in swamps or marshy ground, and 

 finally method of cleaning the fur, a habit common to so many, 

 if not all hairy mammals. 



As to the formation of whorls, feathering and crests on 

 animals, I should submit that the action of underlying 

 muscles exercising traction in diverging directions is the 

 efficient cause in producing them. 



It will be seem that if the dynamical views of the 

 iormation of whorls, featherings, and crests here maintained 

 be accepted, it is an admission that, in a large group of facts 

 of no intrinsic importance, there is evidence that Weismann's 

 great doctrine of the non-inheritance of acquired characters 

 does not hold good. 



