71 



ON THE INHERITANCE OF COAT COLOUR IN THE 

 VARIETIES OF RATTUS RATTUS. 



By J. W. Cutmore. 



[Addendum to Paper in Vol. XXXIII, p. 70.] 



Since the publication of the first part of my article I have 

 completed my experiments on the Rattus group so far as 

 I could with the accommodation at my disposal. 



From an analysis of the results I find : — ■ 



(1) That mating R. r. rattus (black) to R. r. frugivorus or 

 to R. r. alexandrinus (brown), gave an equal number of each 

 colour. 



(2) That mating brown Hybrid to brown Hybrid, off 

 above, gave all brown offspring like themselves. 



Black x Brown. 



Black 50 %. Brown 50 %. First Hybrid generation. 



I I I 



Black Brown Brown 



66|%- 33£%. 100%. Second Hybrid generation. 



(3) That mating black Hybrid to black Hybrid gave 

 eight black and four brown offspring. Six of the black young 

 showed a white mark on the chest, similar to those mentioned 

 by the late Professor Doncaster as indicating the mixed 

 dominant character in his experiments with the common 

 brown Rat, R. norvegicus. Professor Doncaster suggested 

 to me that I should test these so marked ; I am sorry it was 

 not convenient for me to do so. One of the black Hybrids 

 (the male) of the pair that produced both brown and black 

 offspring had a white spot on its chest. 



So far as my experiments went no black offspring were 

 produced from brown Hybrids. I am sorry it was not con- 

 venient for me to test the brown young with white ventral 



