no Experimental Zoology 



erations, however, these characters appear to follow the ordinary 

 Mendelian rules of segregation and gametic purity." Hurst 

 calls attention to the similarity of these results to those of Cuenot 

 with spotted mice. The results are in agreement as far as the 

 marked coat is a unit-character following Mendelian Hnes, and in 

 so far as it may be carried by albinos in a latent state. The two 

 results differ in that the marked coat in mice is completely re- 

 cessive to uniform coat, while the Dutch markings in rabbits are 

 neither dominant nor recessive at first, but give variable hybrids. 

 Castle has made a few experiments with rabbits, but the re- 

 sults gave little that was new in principle. "A cross between 

 two different types of albino rabbits, Himalayan and pure white, 

 shows imperfect dominance of the Himalayan character in the 

 offspring, but complete segregation among their gametes." 

 Long-haired rabbits bred to short-haired individuals give off- 

 spring with short hair. When rabbits with ears of different 

 length are mated, the offspring have ears intermediate in length. 

 In this character, blending appears to take place, and neither 

 dominance nor segregation. 



Experiments with Rats 



Rats have been used much less than mice, and the results seem 

 to be more complicated. Crampe has pubhshed the results of 

 a large number of experiments, extending over ten years ; but as 

 the experiments were made before the importance of Mendel's 

 theory was appreciated, it is difficult to interpret from this point 

 of view the data obtained. No more striking instance could be 

 given of the insight into cross-breeding experiments furnished 

 by Mendel's law than a comparison of the work before and after 

 this period. Confused and irregular as the earlier results appear, 

 they arrange themselves into orderly groups in the light of this 

 law. It is, of course, difficult now to show in all cases that Men- 

 del's law unravels Crampe 's results, since the records are often 

 incomplete on important points, where further tests are requi- 

 site to interpret the result. Nevertheless Bateson's analysis 

 of Crampe's data indicates that the outcome shows in many 



