302 STUDIES IN THE EVOLUTION OF ANIMALS 



appear becomes soon extinguished by mixing freely with normal 

 types, would seem to be erroneous. For sex-digitation, instead 

 of being eliminated by dilution, in many instances becomes 

 strengthened. Moreover, the supposition that one monstrosity 

 occurring in a species has no chance of survival must be greatly 

 modified when we know that a whole litter of puppies can at once 

 appear with stump-tails,^ and that almost all the puppies of a sex- 

 digitate Bitch were born with a similar feature. It is evident that 

 there would be ample opportunities for these similarly affected 

 animals to interbreed, and further fix and perpetuate a monstrosity, 

 even if we did not know that, in some cases, dilution with normal 

 blood will not wipe it out. 



Many other monstrosities besides sex-digitation have been 

 transmitted to descendants. That quoted by M. Guinard on p. 

 162^ is a most curious one. A male Guinea-Pig was kept for a 

 long time in the laboratory of the Veterinary School of Lyons. It 

 had no sign of eyeballs, although the orbital cavities were well 

 formed. After death, it was found that there was no trace of 

 optic nerve, and the foramen for its passage did not exist. 

 Otherwise this anomalous Guinea-Pig was healthy and vigorous, 

 and it lived for a long time. It was kept among normal female 

 Guinea-Pigs, and had numerous children. Among them were found 

 six which, like the father, had no eyeballs ! M. Guinard adds : 



' M. Desfosses a demontr^ que cette conformation des organes 

 de la vue est normale chez le Protee.' 



Hairlessness of the body is found ' normal ' in the hairless race 

 of Chinese Dogs, but it has also occurred anomalously in the Horse, 

 the Ox, and the Dog. Even Birds have been met with which had 

 no feathers. So that we begin to suspect that the hairlessness of 



^ I have known of two Bitches, in different countries, which gave a whole litter of 

 puppies with stump-tails. ^ Precis de Teratologie. 



