408 H. H. Newman and J. T. Patterson. 



It seems probable from our studies of the ovaries that the ten- 

 dency to polyembryony is inherent in the unfertihzed egg, which 

 is the seat of a developmental vigor somewhat more intense than 

 that exhibited in the ova of other mammals. This extra expresses 

 itself sometimes by parthenogenetic divisions and at other times 

 in the formation of fairly regular morulae within the confines of 

 the Graafian follicles. That polyembryony is simply a more nor- 

 mal expression of the same superabundant energy in the female 

 germ cells seems highly probable, and we would offer this as a 

 tentative explanation of the physiology of polyembryony, pending 

 an exhaustive study of a large collection of ovaries. 



Taking it for granted then that sex is determined in the undi- 

 vided oosperm, the question naturally arises as to which of the 

 two germinal elements is the sex determiner. Cytological exam- 

 ination of the ovaries reveals no dimorphism of the ova. They all 

 have 32 chromosomes and are equally alike in other respects. 

 The possibility that sex might depend on which of the two ovaries 

 produced the egg that became fertilized as suggested by the work 

 of Dawson ('09) . This writer maintains on observational grounds 

 that in the human being the male producing ova come from the 

 right and th^ female producing ova from the left ovary. The cor- 

 pus luteum served to indicate which ovary functioned in any given 

 pregnancy. In the armadillo we have an exceptional opportunity 

 to put Dawson's theory to a test, for the corpus luteum of this 

 species is a very prominent feature of the ovary that has func- 

 tioned. A study of our data reveals the fact that the corpus 

 luteum is found with almost equal frequency in right and left ova- 

 ries, which coincides with the exact equality of male and female 

 litters. Unfortunately for the theory, however, there is no cor- 

 relation between the sex of the embryos and the dextrality or 

 sinistrality of the functional ovary. Out of twenty cases in which 

 the right ovary contained the corpus luteum, the sex of the em- 

 bryos was male in seven and female in thirteen; while out of 

 thirteen cases in which the left ovary held the corpus luteum, 

 the sex was male eight times and female five. Evidently then 

 the position of the functional ovary has no determining influence 

 on sex. 



