106 Experimental Zoology 



guinea pigs was produced, which compared favorably with the 

 intermediate groups described above. Crossed with long-haired 

 individuals two kinds of offspring were produced, with long and 

 intermediate hair, but with no definite line of separation. 



Experiments with Rabbits 



Hurst has carried out a series of experiments with rabbits that 

 have given results of unusual interest, especially in connection 

 with the inheritance of color and of length of hair. Two races 

 that were known to breed true were used, namely, white An- 

 goras and Belgian hares. The former is an albino breed with 

 pink eyes and silky hair. These animals have a peculiar habit 

 of swaying the head when at rest. The Belgian hare has a pig- 

 mented skin, dark eyes, and short yellow-gray fur. When crossed 

 the hybrids were pigmented like the Belgian hares, but the hair 

 had lost the yellow color and was gray, like that of the common 

 wild rabbit. When these first hybrids were inbred they produced 

 14 distinct types in the second generation, viz. : 



1. Hair short, pigmented, gray, uniformly colored. 



2. Hair short, pigmented, gray, marked. 



3. Hair short, pigmented, gray, Dutch marked. 



4. Hair short, pigmented, black, uniform. 



5. Hair short, pigmented, black, marked. 



6. Hair short, pigmented, black, Dutch marked. 



7. Hair short, albino, white. 



8. Angora, pigmented, gray, uniform. 



9. Angora, pigmented, gray, marked. 



10. Angora, pigmented, gray, Dutch marked. 



11. Angora, pigmented, black, uniform. 



12. Angora, pigmented, black, marked. 



13. Angora, pigmented, black, Dutch marked. 



14. Angora, albino, white. 



This " epidemic of variation" in the second generation of hybrids 

 has been the common experience of experimenters both in ani- 

 mals and plants, and before the Mendelian principles became 



