434 Mr. Hammond and Dr. Marshall. Correlation between 



Put to male. 



First notes made on litter. 



Sept. 27, 1910 



Oct. 29, 1910 

 Feb. 27, 1911 



Jan. 26, 1911 



Mar. 29, 1911 



Apr. 30, 1911 



June 2, 1911 



July 4, 1911 



July 15, 1911 



Aug. 19, 1911 

 Oct. 6, 1911 



Sept. 2, 1911 



Oct. 25, 1911 



Nov. 27, 1911 



Jan. 12, 1912 



Feb. 15, 1912 



Feb. 15, 1912 



Mar. 17, 1912 



Apr. 11, 1912 



May 13, 1912 



May 17, 1912 



June 19, 1912 



Heape states that 10-15 days is the average duration of the dicestrous 

 cycle, but that some individuals exhibit heat at intervals of three weeks. 



The pro-cestrum is stated to last from one to four days, and oestrus for 

 about a day or longer. During the pro-cestrum the vulva tends to become 

 swollen and purple in colour, and this appearance may continue during 

 oestrus. There is no external bleeding, and it is difficult or impossible to 

 state when the pro-oestrum ends and oestrus begins. It would seem that 

 the two periods are much abbreviated, as in the case of the sheep and 

 many other animals in which the uterine changes characterising the heat 

 periods are slight, as compared with those of the dog or the monkey. 



The uterus may show undoubted congestion at the heat period, but we 

 have never observed any breaking down of vessels or extravasation of blood 

 in the non-pregnant rabbit's uterus, excepting near the end of the pseudo- 

 pregnant period. It is possible that these (or some of these) cases represented 

 the commencement of a pro-oestrous period. Apart altogether from these 

 instances congestion presenting a close similarity to that observed in the case 

 of the pro-oestrous sheep was found to occur in the rabbit's uterus at the 

 time of heat. Pigment formation has not been noticed. Its absence from 

 the uterus of the rabbit suggests that in this animal blood extravasation does 

 not ordinarily take place in the pro-oestrous or cestrous periods. The glands 

 do not show very much evidence of activity during the heat period, and their 

 degree of development is very much less than that shown in the earlier stages 

 of the pseudo-pregnant period. 



Theoretical. 



Many of the observations described above have an important bearing upon 

 certain statements made by Hill and O'Donoghue in a recent paper on the 

 cestrous cycle in the marsupial cat, Dasyurus viverrinus. According to these 

 authors ovulation in Dasyurus occurs at an interval of some days after 

 oestrus, there being a definite post-oestrous period terminating in ovulation. 



