TOO 



THE AMERICAN NATURALIST [Vol. XLIII 



(2) mare covered by more than six different stallions had ten 

 foals, all male; (3) bitch covered by two different stud dogs gave 

 birth in two litters to six male dogs; (4) sow gave birth to a litter 

 of ten boar pigs. In all these cases the female is supposed to 

 have been unilaterally sterile. One might urge against the 

 cogency of these facts as supporting the theory that the law of 

 probability and the hypothesis of Mendelian dominance could 

 explain them as well as the supposition of unilateral sterility. 



In chapter 8 cases of pregnancy are reported to prove the 

 theory. The proof here consists in showing cases of male and 

 female pregnancy with the corpus luteum in the right and left 

 ovum respectively; six cases of the former are given, and three 

 of the latter (one doubtful). Among the vast number of pos- 

 sible cases, those eight might very well be mere coincidences — 

 for when exceptions occur he invokes the aid of a migration of 

 the ovum. 



Chapter 9 considers cases of extra-uterine pregnancy to prove 

 the theory. Twelve cases are reported of tubal pregnancy and 

 a corpus-luteum-bearing ovary on the same side. Accordingly, 

 if pregnancy be in the right oviduct and the foetus a male, one is 

 justified in declaring the ovum eame from the right ovary. Nine 



ra-utcrine arc shown 

 >seow, is said to have 

 lg in the right tube 

 it ovarian pregnancy 



ncy after unilateral 

 after removal of the 

 1 females w T ere born 

 ! is reported of right 

 left ovary, followed 

 *e admitted, but they 



to the 



ight halves of 

 where the left 



