68 LEO LOEB 
In the guinea pig ovulation occurs in the large majority of cases 
without any previous copulation. In many cases however copula- 
tion is not without significance even in the guinea pig; it acceler- 
ates ovulation. While, after delivery, a spontaneous rupture may 
take place without copulation, in other cases it does not occur with- 
out ovulation. Also in the ordinary period of heat ovulation does 
not need to take place without copulation. Copulation is there- 
fore not without importance; but in almost all of these cases ovu- 
lation is only deferred and sooner or later it will take place with- 
out the male. So far as the literature has been accessible to us it 
appears that the role copulation plays had not been fully appre- 
ciated by former investigators. Certain observations which we 
made indicate that other factors besides a preceding copulation 
may influence ovulation, and we intend to continue our investi- 
gation in this direction. 
Our observations enable us to give some data concerning the 
time relations in the growth of various ovarian structures. 
a Follicles. In about six days after ovulation small follicles 
reach medium size. In approximately eight days large follicles 
have developed and now degenerative processes set in. Mitotic 
cell division is most pronounced in the granulosa before degenera- 
tive processes have commenced; but mitoses may still beseen, if 
a slight degree of degeneration exist. 
b Ordinary corpora lutea. The development of corpora lutea 
within the first six days after ovulation has been described in a 
previous paper. At six days we see for the first time, besides the 
capillary vessels, blood vessels with walls consisting of two rows 
of cells penetrating into the corpus luteum; they become some- 
what more frequent from the tenth day on. In the meantime 
mitotic division of lutein cells continues and the increase in these 
cells causes the central connective tissue to become smaller in 
amount. 
In corpora lutea ten to eleven days old a few vacuolar cells are 
present in the periphery of the corpus luteum. From ten to fif- 
teen days after ovulation vacuolization is still very slight in peri- 
pheral luetein cells. From fifteen to eighteen days more fine or 
coarse vacuolization may appear. Other lutein cells are still 
