40 BTLLETIX 1090, U. S. DEPARTMENT OF AGRICULTURE. 



lies shows a situation similar to that found with color, pattern, and 

 polydactylisni. 



Three of the families (1, 9, and 20) produced no abnormalities of 

 any kind. It will be shown later that Family 1 was one of the two 

 poorest families in regard to vigor. It was the second family to 

 become extinct, doubtless because of its deterioration in both fertility 

 and ability to raise such young as were born. The other poorest 

 family, No. 15, produced only two abnormalities. One was no more 

 serious than a tuft of long hair or "mustache" on the right side of the 

 muzzle. The other was an animal in which the legs were rudimentary. 



Turning to the family which was unquestionably the most vigorous 

 between 1906 and 1915, namely, Family 13, we find a considerable 

 number of abnormalities. Aside from 7 animals with "mustaches," 



I with an abnormally small left eye, 1 with the neck twisted to the 

 right, 1 with a hole in the skull through which the brain protruded, 

 and one with the front legs bent back against the body, there were 



II of the well-known cyclopean type of monster. Another cyclops 

 was a crossbred, three-fourths of whose ancestry came from Family 

 13. All of the other inbred families combined produced only 23 of 

 these monsters. Five came from Family 19, 9 from Family 32, 3 

 from Family 35, and the rest from Families 7, 11, 17, and 18. Here 

 again we find evidences of family differentiation, the family most 

 productive in cyclopean monsters happening to be the most vigorous 

 in other respects. 



The distribution of the cyclopeans within Family 13 is interesting. 

 All were descended from a single mating in the second generation. 

 All but two (uncle and niece) were descended from a single mating 

 in the seventh generation. Two were sisters. 



As the 11 cyclopeans in Family 13 had 162 normal brothers and 

 sisters, the variation can not be a simple Mendelian recessive. 

 Nevertheless it seems clear that a tendency to produce it is heredi- 

 tary, segregating out in particular lines of particular families, and 

 that this tendency has nothing to do with the vigor of the stock. 

 One cyclopean monster of an extreme type was produced by the 

 control stock. 



In another type of monster the body was undersized (which was 

 not the case in the cyclopean monsters) and the legs were rudimentary. 

 In extreme cases a leg would be represented externally merely by a 

 single claw to be found only by feeling in the fur. One such case, 

 as already noted, was produced by Family 15. There were 5 in 

 Family 24 and possibly 1 in Family 39. Two of those in Family 24 

 were born in different litters from a single mating in the eighth genera- 

 tion. This mating also produced 16 normal young. Three matings 

 were made among the normal young. Two produced only normals 



