Principles of Heredity 173 



variation is concerned) occasional cases of "mosaics," a 

 phenomenon which has nothing to do with "ancestry." 



3. Colours of Rats and Mice. Professor "Weldon 

 reserves his collection of evidence on this subject for the 

 last. In it we reach an indisputable contribution to the 

 discussion a reference to Crampe's papers, which together 

 constitute without doubt the best evidence yet published, 

 respecting colour-heredity in an animal. So far as I have 

 discovered, the only previous reference to these memoirs is 

 that of Ritzema Bos*, who alludes to them in a consideration 

 of the alleged deterioration due to in-breeding. 



Now Crampe through a long period of years made an 

 exhaustive study of the peculiarities of the colour-forms of 

 Rats, white, black, grey and their piebalds, as exhibited in 

 Heredity. 



Till the appearance of Professor Weldon's article 

 Crampe's work was unknown to me, and all students of 

 Heredity owe him a debt for putting it into general 

 circulation. My attention had however been called by 

 Dr Correns to the interesting results obtained by von 

 Guaita, experimenting with crosses originally made between 

 albino mice and piebald Japanese waltzing mice. This 

 paper also gives full details of an elaborate investigation 

 admirably carried out and recorded. 



In the light of modern knowledge both these two 

 researches furnish material of the most convincing character 

 demonstrating the Mendelian principles. It would be a use- 

 ful task to go over the evidence they contain and rearrange 

 it in illustration of the laws now perceived. To do this here 

 is manifestly impossible, and it must suffice to point out 

 that the albino is a simple recessive in both cases (the 



* Biol Cblt. xiv. 1894, p. 79. 



