Experiments with other Mammals 1 1 1 



cases the Mendelian expectation. Crampe found that when 

 wild gray rats, Mus decumanus, were bred to albinos, the off- 

 spring (Fj) were of two kinds, viz. either (I) gray like the wild rat, 

 or (II) gray with white marks. If the former (I) were bred inter 

 se, the following types appeared : 



1. Self -gray. 



2. Gray with white marks. 



3. White and gray. 



4. White (albino). 



5. Black-and-white. 



6. Black with white marks. 



7. Black without marks. 



If the other group of offspring (II) was used, i.e. inbred, all of 

 the preceding types except 3 (white and gray) and 5 (black-and- 

 white) were produced. 



Bateson states that the great variety of types that appear here 

 is difficult to interpret, but that such occurrences are by no means 

 uncommon. He suggests that two classes of germ-cells may 

 be present either in the albinos or in the wild gray rat. 



The albino is recessive to all the other six types, as shown by 

 crossing these with albinos. The extracted albinos bred inter 

 se, whatever their origin, gave only albinos. In this connection 

 Crampe makes another statement -of interest. Albinos that 

 had been bred true for several generations behaved differently 

 from extracted albinos. The former albinos were simply re- 

 cessive on being crossed with colored rats, while the extracted 

 albinos gave a mixture of ancestral types when crossed with 

 colored types. The result appears to be similar to Cuenot's 

 with mice where the ancestry of the albino appears as a factor 

 in the product. 



On breeding inter se each of the seven types given above (F-^, 

 Crampe found that the offspring (F 2 ) belonged to the following 

 types : 



Type i might give types 12 4 67 



Type 2 might give types 1234567 



