SPECIAL CREATION OR DERIVATION? 



by adults of allied species, but which, having no 

 functions to discharge, are after a while absorbed 

 or dwindle into mere rudiments. The mamma- 

 lian embryo at first circulates its blood through 

 a vascular system like the gills of fishes ; after- 

 wards this is replaced by a vascular membrane 

 called the allantois, like the membrane which 

 replaces gills in the development of birds and 

 reptiles. Neither of these structures is useful to 

 the embryo for the purpose of aerating its blood, 

 and there is no possible explanation of their 

 appearance in untold millions of mammals, un- 

 less we admit that they are due to inheritance 

 from the amphibious ancestors of the mamma- 

 lian class. Of like meaning are such facts as the 

 presence of useless teeth in the jaws of foetal 

 whales, and in the beaks of certain embryonic 

 birds ; the rudiments of a pelvis and hind-limbs 

 in many snakes ; the wings, firmly fastened 

 under their wing-cases, in insects which do not 

 fly ; the cascum, or blind intestine, and the ter- 

 minal vertebrae in man ; and the incisor teeth 

 in calves and other ruminants, which never cut 

 through the gum. No explanation can be given 

 of such phenomena, save on the theory of in- 

 heritance ; for the pompous statement, which 

 we sometimes hear, that such organs have been 

 created " for the sake of symmetry, and in order 

 to complete the scheme of nature," is no expla- 

 nation at all. As Mr. Darwin pertinently asks. 

 397 



