14 



GENETIC STUDIES OF RABBITS AND RATS. 



in ear-length from 81 to 88 millimeters, Himalayan from 92 to 97 

 millimeters or about 1 centimeter longer-eared than Polish, while 

 the three Flemish individuals used as parents, notwithstanding their 

 diversities in weight, are remarkably uniform in ear-length, ranging 

 from 143 to 147 milUmeters, or about 6 centimeters greater than 

 Polish and 5 centimeters greater than Himalayan. The three races 

 are very distinct and each by itself very uniform. 



The data on the ear-length of the cross-bred rabbits is summarized 

 in table 4 and is shown graphically in figure 7. 



S J>» J.6.7.8.9 aO.I .S J* .5.6 .T.e.SIOfi.l .2.3 .* .S.6 .7 .fl .9 11.0,1 .Z .3 .*.S.6 .7 .8.9 itO J .2 .3 A .S .6 .7.8.9 ao.l.2.3 A .5.6 .7 .B .9 l«.l Z 3 AS 6 n ^ 



EAR LENGTH, IN CENTIMETERS 



Fig. 7. — Polygons showing variation in ear-length of the three pure races of rabbits and of their 



Fl and F2 hybrid offspring. 



In the cross between the Polish and Himalayan breeds, which 

 differ in ear-length by about 10 millimeters, long ear appears to be 

 completely dominant. Variation is about the mode of the Himalayan 

 race and the average is practically the same (94.8 in the Himalayan, 

 94.9 in the Fi group). But in Fa the variation is much greater and 

 the range extends downward so as to include the mode of the Polish 

 race as well as upward to cover the entire range of the Himalayan 

 race and of Fi. 



The cross of Himalayan with Flemish gives results which are easier 

 to interpret. These two races considered singly are very uniform in 

 ear-length. Each varies closely about a mode widely separated 

 from that of the other race (see fig. 7). Fi is about 4 or 5 millimeters 

 below the intermediate and varies little. F2 has the same relation 

 to the intermediate, with practically the same mean, but is much 

 more variable, the standard deviation (table 4) having risen from 

 2.08 millimeters in Fi to 5.85 millimeters in F2, and the range from 8 

 millimeters to 24 millimeters. Nevertheless, the range of F2 does not 



