CH. iv PRESENCE & ABSENCE THEORY 27 



mice, and eye colour in man are but a few examples 

 of the diversity of characters which all follow the 

 same law of transmission. And as time went on 

 many cases which at first seemed to fall without the 

 scheme have been gradually brought into line in the 

 light of fuller knowledge. Some of these will be 



FIG. 2. 



A wing feather and a contour feather of an ordinary and a silky fowl. The peculiar 

 ragged appearance of the silky feathers is due to the absence of the little hooks 

 or barbules which hold the barbs together. The silky condition is recessive. 



dealt with in the succeeding chapters of this book. 

 Meanwhile we may concern ourselves with the single 

 modification of Mendel's original views which has 

 arisen out of more ample knowledge. 



As we have already seen, Mendel considered that 

 in the gamete there was either a definite something 

 corresponding to the dominant character or a definite 

 something corresponding to the recessive character, 



