No. 580] 



NOTES AND LITERATURE 



L>55 



the capacity to fertilize eggs and sire young. There are further reasons 

 for concluding that the motile sperm of the hybrid males may be physio- 

 logically different from those of the normal guinea-pig, for it often re- 

 litters were unexpectedly small. 



It may be added that sterility was not due to the absence of sec- 

 ondary sexual characters, for all the males were normal in this 

 respect. 



The percentage of fertile males in each generation from the 

 back crosses above described, was as follows: 



I\ F, F, F 4 F e F. F, . 



1/2 Wild 1/4 Wild 1/8 Wild 1/16 Wild 1/32 Wild 1/64 Wild 1/128 Wild 



0.0 0.0 14.29 33.32 60.67 69.39 73.33 



In the generations having the more dilute wild blood the percent- 

 age of fertile males increased. The author holds that some dis- 

 turbance occurred in the Lrainetou'enesis of the males, subsequent 

 to hybridization. The females were normal, but they transmitted 

 this disturbing element to their sons. However, by back-cross- 

 ing with guinea-pigs this peculiar quality was segregated out. 

 It is evident that if the heredity of fertility and sterility in this 

 case is Mendelian. it is due not to one or two allelomorphic pairs 

 of factors, but to multiple factors. A table is given of the per- 

 centages of ultimate receseuYes expected in back crosses on the 

 basis of various numbers of factors involved. The series for 8 

 factors, given below, approaches most nearly the percentage of 

 fertile males obtained (see above) : 



F t F 2 F 3 F 4 F B F, F t 



0.0 0.39 10.1 34.36 59.67 77.58 88.16 



The application is somewhat misleading, as the author states, 

 since the probable errors are not given. In each generation the 

 probable error would have to be calculated on the supposition 

 that the females of the preceding generation were normally dis- 

 tributed, otherwise one would have to take into account the error 

 of all the preceding generations. It is improbable that the fe- 

 males of any generation, except F,, were normally distributed. 



He concludes that fertility acts as a very complex recessive 

 character, the results being in accord with the expectations if a 

 number of dominant factors for sterility were present. After 

 these dominant factors were eliminated, there would be produced 

 a fertile recessive type. 



Byron B. Horton 



