NUMBER OF OVA: ALBINO RAT 445 
in the rat, and Rubaschkin (’05) in the guinea-pig, stated that 
ovulation occurs spontaneously during heat and is independent 
of coitus. Iwanoff (00) showed that in the rabbit pregnancy is 
also possible by the artificial insemination, and Heape (’97) tried 
artificial insemination on mares, donkeys, and cows, and suc- 
ceeded in producing pregnancy in all. 
Loeb (711) also believes that in the guinea-pig ovulation occurs 
in the large majority of cases independently of copulation. 
Marshall and Jolly (05), in the dog and in the ferret, described 
the spontaneous ovulation at each of the earlier heat periods 
during the breeding season. 
To test this matter in the albino rat, I used the control females 
employed in a study of the surviving ovary after semispaying. 
These control female rats were separated from the males at 
twenty days of age, and were kept together with the semispayed 
rats of the same litter. Nevertheless, in the ovaries of these 
two control rats were found corpora lutea at sixty-two and sixty- 
nine days, respectively; that is, ovulation occurred spontaneously 
without any association with the male. From all these results 
there is little doubt that in the majority of mammals ovulation 
occurs regularly during the oestrus period and is independent of 
copulation. 
Although many investigators have studied the relation be- 
tween menstruation and ovulation in the higher mammals, such 
as the monkey and man, yet whether ovulation occurs before, 
during, or after menstruation has not been determined. It fol- 
lows, therefore, that at least in monkeys, as well as in man, the 
process of ovulation does not seem to be necessarily associated 
with menstruation, though such a statement is not definitely 
made by most of the observers. 
According to Heape (98), ovulation and menstruation are not 
associated, since in monkeys menstruation may occur periodi- 
cally all the year round, but the season for ovulation and concep- 
tion is limited. Van Herwerden (’06) has also given further evi- 
dence that there is no close connection between ovulation and 
menstruation, either in monkeys or in the aberrant lemur, Tar- 
sius spectrum. 
