IN NATURE of Jan. 10, Prof. MacBride appears to deny that a cross between two types of Cavia to which I referred, and which leads to Mendelian segregation, was an interspecific cross. Not only did Detlefsen,1 who carried it out, regard it as such, but, also, the male hybrids were wholly sterile. In view of the latter fact, I did not suppose that Prof. MacBride would question its interspecific nature.
Detlefsen, Pub. 205, Carn. Inst. Wash.