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THE AMERICAN NATURALIST [You LIV 



made, namely, of the normal offspring resulting from the 

 mating of homozygous to heterozygous individuals. The 

 expectation in this case is equality of the classes, and the 



TABLE V 

 Matings NN X Nn 



Observed . 



actual numbers found in the 25 tests made were 14 NN 

 and 11 Nn, the expectation in this case being 12.5 in each 

 class (see Table V). 



Additional evidence that the extracted homozygous 

 normals are free from palsy ' 'taint " is furnished by three 

 matings of such animals together, from which 31 living 

 offspring have been obtained, all normal. 



The foregoing data would appear to be sufficient in 

 number and in closeness of ratios to demonstrate conclu- 

 sively that congenital palsy in guinea-pigs is inherited in 

 simple Mendelian fashion and depends on a single unit 

 difference, the normal condition being completely dom- 

 inant to the heterozygote. 



Symptoms 



A brief description of the typical symptoms has al- 

 ready been given, but for comparison with the same or 

 similar conditions which may be observed by others, it 

 seems desirable to describe the symptoms of the palsy as 

 it occurs in our stock in somewhat greater detail. 3 



A word ought perhaps to be said at this point about the 

 use of the term congenital palsy. The congenital part is 

 evident enough and needs no explanation further than to 

 point out that we use it in the sense of being present at 



