REPRODUCTIVE CYCLE IN DASYURUS VIVERRINUS. 161 
lasts into the first fortniglit in August (i.e. it extends over 
the Avinter months). 
The male does not appear to experience a marked rutting 
season. 
Copulation is similar to that of Didelphys (Selenka), and 
the sperms can remain alive in the Fallopian tubes for at 
least two weeks. 
Anoetrus. — The ancestral period lasts more than half the 
year. 
Pro -oestrus. — Pro-oestrus appears to extend over a vary- 
ing period of from four to twelve days. 
During this time, the lips of the cloaca become swollen, the 
pouch enlarges somewhat and becomes slightly tumid and 
moist, and the Grraatian follicles increase in size and become 
vesicular. The uterine mucosa increases in thickness and 
becomes more vascular, its glands lengthen and become con- 
voluted and the uterine epithelium also tends to thicken. 
CEstrus. — CBstrus lasts usually for one or two days and is 
the period during which copulation occurs. 
The changes already initiated during pro-oestrus in the 
various parts of the reproductive system are continued with- 
out interruption. 
Post-oestrus. — Post-oestrus, Avhich term we employ to 
designate the period following oestrus and terminated by 
ovulation, occupies as a rule about five or six days. 
The tumidity of the cloacal lips disappears, but the changes 
in the pouch and uterus still continue, not, however, very 
actively. 
In the ovary (1) the ova give off the first polar body 
and the spindle for the second meiotic division is formed. 
(2) The follicles attain maturity and ultimately rupture, 
setting free the ova. 
Ovulation. — Ovulation marks the end of this period and 
occurs generally about five or six days after oestrus. It is 
spontaneous and independent of copulation and is remarkable 
because of the large number of ova liberated. Ovulation is 
succeeded (a) by pregnancy or (b) by pseudo-pregnancy. 
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