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THE AMERICAN NATURALIST [Vol. LI 



II. The Inheritance of Spotting in Rats 

 Castle's work on tlie inheritance of fluctuations in the 

 hooded coat pattern of rats is well known to all geneti- 

 cists, and may now be considered in an attempt to examine 

 the bearing of spotting on the inheritance of fluctuating 

 characters in general. The hooded rats with which 



Castle worked have been shown clearly by Doncaster, 

 Mudge, and others, as well as by Castle himself, to be 

 recessive to self or solid colored coat in inheritance. The 

 hooded pattern is, however, subject to wide fluctuation 

 producing a series of rats from those with the whole 

 dorsal surface and most of the ventral surface pigmented, 



