388 



HELEN DEAN KING 



4. Female no. 4, spayed on the left side, was mated with a 

 male which lacked the right testicle. The litter produced con- 

 tained six young ; two of which were males and four were females. 



These results show conclusively that eggs from either ovary 

 of the albino rat can be fertilized with spermatozoa from either 

 testicle. They also prove that males can be produced when the 

 right gonads are lacking in the breeding animals and that females 

 can develop when the left gonads of the breeding animals have 

 been removed. 



Table 2 gives a summary of the distribution of the sexes in all 

 of the young produced by the four semi-spayed females. 



Table 2 



The most striking fact brought out in the above table is that 

 the litters average but 4 . 64 young each ; a result which can doubt- 

 less be justly attributed to the removal of one of the ovaries from 

 each of the breeding females. It is very probable that in the rat 

 ovulation takes place in both ovaries at the same time, and that 

 the litter of a normal female contains young that have developed 

 from eggs derived from each ovary. Presumably, therefore, the 

 removal of one ovary would cause a decrease in the size of the 

 litter by lessening the number of eggs that might have been fer- 

 tilized at the same time. 



The average number of individuals in the 30 litters of albino 

 rats examined by Cuenot was 8.03; while the 80 litters I have 

 obtained contained an average of only 5 . 6 young. My records, 

 however, are made up in great part from litters produced in 



