No. 633] INHERITANCE IN THE OSTRICH 305 



trated attention wholly on the germ plasm as the source 

 of heredity and variation in the animal world. Ordi- 

 narily in studying the origin of characters we start with 

 the germ and consider how factors arise and characters 

 come to be formed from them ; but there is no reason why 

 we should not also contemplate their origin by observing 

 their manner of appearance in the soma, and from this 

 try to understand their transmissibility. Even if hitherto 

 the former has alone proved fertile in results and the 

 latter sterile it does not follow that renewed attacks on 

 the problem with additional armament will always fail. 



Callosities are a definite response of the skin to stimuli 

 resulting from contact with some hard substance involv- 

 ing pressure and friction. They involve new inter-rela- 

 tionships of the structures concerned, and may affect the 

 underlying tissues and even the bone on which they rest. 

 On the factorial hypothesis the multitude of character- 

 istics making up the complex organism are assumed to 

 have a measure of independence; yet it is allowed that 

 definite hereditary inter-relationships exist among them 

 when we contemplate the body as a whole. May not some 

 of the characteristics be directly factorial and others a 

 result of the inter-relationships brought about in their 

 establishment, just as in architecture certain subsidiary 

 structural parts have to be introduced in order to admit 

 of some major effect. 10 In any structural change, how- 

 ever simple, and whether germinal or somatic in origin, 

 the complex tissue inter-relationships of the organism 

 are involved. The old ties are disturbed and new ones 

 are es-tablished. It is conceivable that a continuance of 

 the application of fresh stimuli, from generation to gen- 

 eration, may result in a weakening of the old relation- 



10 Mr. L. Doncaster (" Heredity/ ' Cambridge, 1911, p. 97) expresses 

 much the same idea when he says: "The belief that 'somatic" .-hange* 



determined by a 'factor' or determinant in the germ-cell, but it is clear 



