144 MENDELISM CHAP. 



variations of living forms in terms of definite physiological 

 factors, and the diversity of animal and plant life is due 

 to the gain or loss of these factors, to the origination of 

 new ones, or to fresh combinations among those already in 

 existence. Nor is there any valid reason against the sup- 

 position that even the most remarkable cases of resem- 

 blance, such as that of the leaf insect, may have arisen 

 through a process of mutation. Experience with domestic 

 plants and animals shows that the most bizarre forms may 

 arise as sports and perpetuate themselves. Were such 

 forms, arising under natural conditions, to be favoured 

 by natural selection owing to a resemblance to something 

 in their environment we should obtain a striking case 

 of protective adaptation. And here it must not be for- 

 gotten that those striking cases to which our attention 

 is generally called are but a very small minority of the 

 existing forms of life. 



For that special group of adaptation phenomena classed 

 under the head of Mimicry, Mendelism seems to offer 

 an interpretation simpler than that at present in vogue. 

 This perhaps may be more clearly expressed by taking a 

 specific case. There is in Africa a genus of Danaine 

 butterflies known as Amauris, and there are reasons for 

 considering that the group to which it belongs possesses 

 properties which render it unpalatable to. vertebrate ene- 

 mies such as birds or monkeys. In the same region is 

 also found the genus Euralia belonging to the entirely 



