WHEN CHARACTERS ARE COMBINED 



13 



coats of guinea pigs show black, white, chocolate, yellow, or 

 a mixture of certain shades of these different colors. For 

 instance, spots of yellow-red and of blue-black, also dashes 

 of black and of white, often occur in different combinations. 

 But no combination of colors taught Dr. Castle plainer lessons 



Guinea Pigs and their Descendants 



A dark, smooth mother and a rough albino father are at the top. Below is their son. 

 He is black because, in guinea-pig inheritance, black is dominant over white ; he is 

 rough because rough coat is dominant over smooth coat. At the bottom is a smooth, 

 white grandchild of the black and the white grandparents. (After Castle, 1905.) 

 Publication 23, Carnegie Institution 



of inheritance than those which he learned from guinea pigs 

 that were plain black and plain white. Still, even these were 

 more or less interesting according to another character of 

 the coat that covered them. For some the coat was rough as 

 a rug, with spots here and there that looked like " cowlicks " 



