INSEPARABLE EFFECTS 37 



y is common to three of the four groups, and therefore 

 must be carried by dilute cinnamon-agouti, the fourth. 

 The differentiating characters in the set are therefore 

 X and X and Z and z ; and, since three of the four 

 possible combinations made by these characters are 

 already appropriated, the fourth, Xz, must belong to 

 dilute cinnamon-agouti, whose three characters are 

 therefore Xyz. 



Thus the complete set of eight groups formed by all 

 the possible combinations of the three pairs of characters 

 X and X, Y and y, and Z and z, are : 



Still another example of inseparable effects is dis- 

 closed in the experiments on the colours of rabbits 

 carried out by Mr. C. C. Hurst, and Professor Castle of 

 Harvard. Both experimenters were more interested in 

 albinism and colour patterns, but the data concerning 

 these may be neglected and those for the colours them- 

 selves, which were reported at the same time, considered 

 separately. 



A black rabbit is sometimes found among common 

 wild grey rabbits, more especially in places where the 

 wild race has been mixed with the tame ; and young 

 black rabbits have been found in wild litters which 

 could be the progeny of grey parents only upon both 



