COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 63 



Leaving out of consideration the degree in which the rough character 

 is developed in the coat of hybrid offspring, we may inquire how nearly 

 the Mendelian proportions of rough and smooth young are approxi- 

 mated. This will be plain from an examination of the following table : 



As in the case of albinism, there are a few more recessive individuals 

 than are expected. This may be purely a chance result, or it may be 

 due to superior fertility of the recessive gametes ; but a different expla- 

 nation is suggested by an observation which will presently be stated. 

 The suggested explanation is that the excess of recessive individuals 

 may be due to latency of the rough character in certain individuals 

 apparently smooth. That such latency is possible is shown by the 

 sudden appearance in one of my families of smooth animals of a partial 

 rough individual, 9 969, having a well-marked crest extending from 

 the head to the middle of the back and conspicuous though imperfectly 

 developed side rosettes. The ancestors of this female for at least three 

 generations had been ordinary smooth individuals, though it is possible 

 that one or more of these may have had a slight crest in the region of 

 the shoulders; for I found that a brother of 9 969, viz, c? 971, had 

 such a crest, though it could be detected only by very careful examina- 

 tion. Unfortunately most of the ancestors had died before my attention 

 was called to this case. The father's skin, which I have, shows no 

 indication of a crest, though possibly it might have done so before it 

 was dried. The partial-rough 9 969 had by the brother mentioned, 

 c? 971, four young, one of which was a partial-rough like herself, the 

 others being smooth. Clearly, then, she both possessed the rough 

 character in a state of partial activity and was able to transmit it in 

 this condition to her offspring, though in her ancestors it must have 

 been present in a state of almost, if not quite complete latency. Very 

 likely suitable matings of the mother would restore the rough character 

 in certain of her offspring to a condition of full activity. Further 

 experiments with this animal are now in progress. 





