68 HEREDITY AND EUGENICS 



Scottish terriers, but since a certain dog occurs in 

 both the male and female ancestral lines the outcrop 

 of spotting would be accounted for if that animal 

 were carr34ng a recessive factor for spotting. In the 

 other case, four spotted puppies occurred in tw^o 

 litters of pedigree Airedale terriers. The pedigree 

 of the five previous generations shows that one male 

 occurred seven times and one female three times in 

 this pedigree, the former occurring on both sides of 

 each ancestral line. He was probably carr3"ing a 

 recessive factor for spotting, or possibly a mutation 

 giving rise to this factor took place in his gametes. 



The wTiter (Gates, igoga) found in a cross between 

 a pure-bred Old Enghsh sheep dog and a Scotch 

 collie that F^ dogs were produced wdth several dif- 

 ferent lengths of tail, or no tail, like the mother, and 

 with many other differences in coat, build, and 

 temperament. It is probable that almost all our 

 pedigree breeds of domestic animals carr}^ some 

 recessive characters, w^hich have never been eliminated 

 since the original crosses, which in man}^ cases w'ere 

 the foundation of the breed. But these germinal 

 difi"erences must have arisen at some time through 

 germinal changes which gave rise to the parental t3^pes, 

 although similar germinal changes may equally well 

 occur afterwards and be carried as recessives in the 

 germ plasm until a cross or inbreeding brings them out. 



The Pearson monograph includes also a study of 

 peculiarities of vision, such as night-blindness, as 

 well as the hair, of albinotics, and also albinism in 

 various animals. Complete albinos wdth pink eyes 

 are known to occur in " pure " races of man, just 

 as they occur in many mammals,* birds, and plants 



* There are records, for example, of albino beavers, chipmunks 

 {Tamias), squirrels, woodchucks {Arctomys), robins {Turdus 

 migratorius\ and sparrows. Dean (1903) says: "True albinos 

 occur among hag-fishes, and partial albinos are not rare." 



