INHERITANCE OF ABNORMAL VENATION. 



17 



TABLE 20. Relation between degree of 

 abnormality in parents and percent- 

 age of abnormal offspring. 



It will be convenient in the present discussion to adopt the following 

 symbols: Ai denotes a fly that is abnormal in one wing only; A2, a fly 

 abnormal in both wings, and C. S. 

 (coefficient of symmetry) that per- 

 centage of a given lot of abnormal 

 flies which are abnormal in both 

 wings. Tables 20 and 21 may be 

 summarized as follows: Flies which 

 are so abnormal that both wings are 

 affected not only gave, on the aver- 

 age, a greater percentage of abnor- 

 mal offspring than flies abnormal in 



only one wing, but the abnormal offspring of the former were more 

 likely to be abnormal in both wings than those of the latter. It must 



TABLE 21. Relation between parents and offspring with respect to one wing or both 



being abnormal. 



only.] 



be noted that this was only "on the average. " Although it was an 

 exceptional case, we have seen that all the offspring of mating 405 

 were normal. The parents each had 



1 'great' ' abnormality in both wings TABL J? 22 r ^lation between parents and 



. T offspring with respect to which wing 



From table 22 it seems evident is abnormal. 

 that a given asymmetry (abnormal r A B = Abnormal in right wing oni y; A u =Abnor- 



. ,, . , , , T ! mal in left wing only; A 2 =Abnormal in 



in the right Wing Only Or abnormal both wings; A! -Abnormal in one wing 



in the left wing only) is not inher- 

 ited. The offspring of a parent 

 which is abnormal in the left wing 

 only are as likely to be abnormal in 

 the right as in the left wing, and 

 vice versa. This is in accord with the 

 results obtained by Castle (1906a) 

 for polydactylism of guinea-pigs, 

 Larrabee (1906) for the reversed 

 optic chiasma of fishes, and Priz- 

 bram (1907) for eye-color of cats. 



As was pointed out, all attempts 

 to fix any particular form of abnor- 

 mality by selection and inbreeding (pure lines?) have failed ; nor has 



