58 CROSSING. 



genes must, according to Davenport have been a factor in the 

 evolution of these breeds. 



So long as we held the view that the inherited things, the 

 genes, were determinants for characters, bound up with these 

 characters in an unvarying relationship, there was indeed no 

 other way out of the difficulty. We know, that those curiously 

 looking chickens which have the feathers reversed and curving 

 outward, have a gene more than normally feathered. If we 

 think of this gene as a determinant of the peculiarity, if we be- 

 lieve it to be in itself responsible for the character, we will have 

 to admit that it has come from nowhere, as we cannot find 

 records of wild chickens with such a curled plumage. We know 

 that polydactily is dominant. If we hold the view, that the 

 gene which in polydactylous chickens determines the aberra- 

 ton is a real determinant for this character in Weismann's 

 sense, we will have to assume that it has been created de novo, 

 as all the wild gallidae have only four toes. We find that black 

 colour is dominant to the colour of Callus bankiva. But there 

 are no wild black species of Gallus. Also we do not know buff 

 wild chickens, or bare-necked ones, or chickens with top-knots. 

 So long as we look upon the genes, which determine the differ- 

 ence between animals with all these new characters and their 

 relatives without them, as upon the exclusive cause of these 

 novel adornments, we will have to be content with the idea 

 that they must have been acquired from nowhere, that a 

 special creation was responsible for the origin of each of them. 



From the moment we take a biomechanical view of the facts 

 of Genetics, the difficulty disappears. The characters of an 

 individual are determined by the way in which it developed, 

 and the way in which an organism develops is determined by a 

 host of factors, of which some are material and constituents of 

 the protoplasm of all the cells, the inheritable factors, genes, 

 whereas others are of a different nature, together constituting 

 the environment. 



A given gene may or may not influence the development, 

 and this the characters of an organism in whose cells it occurs. 



