INHERITANCE OF A BI-LOBED EAR 



Richard Schofield 

 Department of Zoology, University of California 



IN a family in which a bi-lobed ear 

 has been transmitted through four 

 generations, only the right ear shows 

 the characteristic in question. The 

 line of separation does not parallel the 

 vertical axis of the body, but tends to 

 follow the posterior m.argin of the ear. 

 There is no regularity in its manifesta- 

 tion so far as generations are con- 

 cerned, and it appears in either sex, and 

 in both sexes in the same family. Its 

 appearance is not constant, for it may 

 skip one or even two generations and 

 then be present. 



In the individuals designated in the 

 chart by A there is a very marked deep 

 cleft that is of considerable length, while 

 in those marked by B the cleft is not so 

 well marked, and in the case designated 

 by BB it is so slight as to be nothing 

 more than a furrow. In the individuals 

 Bl and B2 there is a deficiencv in hear- 

 ing in the bi-lobed ear, while in the 

 others there is no apparent deficiency 

 of any kind. No information is obtain- 

 able as to when this strange anomaly 

 was first noticed in the family, but 

 in each individual affected the trait is 

 as pronounced at birth as at any other 

 time, and it does not increase with the 

 age of the person. Each case charted 

 has been seen by the writer except the 

 fem.ale shown in the first generation. 

 The cleft probably originated as a 

 mutation, though nothing definite can be 

 said in this regard ; and from its mode of 

 transmission it appears to be an imper- 

 fectly dominant trait. 



In the Journal of Heredity, Decem- 

 ber, 1916, there appeared an article by 

 A. E. Jenks, "Pitted Ear Lobes of Con- 

 genital Origin," in which a condition is 

 described similar to the present case. 

 The author evidently thinks that there 



is at least a possibility of the trait being 

 the result of a mutation which first 

 appeared three gene'^ations p-evious to 

 the one he has described. The cha'-ac- 

 ter, like the present one, appsars to be 

 transmitted as an imo3rfect dDminant. 



In the case at hand there is exhibited 

 a variable inheritance which ranges 

 from the deep cleft in one instance to 

 the slight furrow in another individual. 

 The imperfection of dominance may 

 well be explained by the variability of 

 the potency of determiners, or perhaps 

 as the result of environmental factors. 



OUTLINE OF EAR 



Although every individual affected 

 did not present quite the same charac- 

 teristics, the above drawine shows 

 graphically the striking division of the 

 lobe. (Fig. 19.) 



517 



