THE DEVELOPMENT OF THE CORPUS LUTEUM. 199 
of its resulting to a large extent from the simple hypertrophy 
of certain of its constituent cells, namely, those which com- 
prised the epithelium of the ripe follicle. The wonderful 
property which these cells possess of enlarging within a very 
short time of the follicle’s rupture, a rapidity which seems to 
be especially marked in the case of the sheep’s corpus luteum, 
is apparently without parallel in the histology of the Verte- 
brata, This unique characteristic becomes additionally in- 
teresting when considered in relation to Pfliiger’s hypothesis, 
since supported by Schafer and others, that the cells of the 
follicular epithelium have a totally different origin from 
those belonging to the thecal tissue, being in fact derived 
from the same group of cells as that from which the ova 
arise. 
PostTscRIPT. 
Heape, in a recently published paper, describes the forma- 
tion of the corpus luteum in the rabbit as follows :—“ The 
corpus luteum is formed by the ingrowth of cells surround- 
ing the follicle together with the follicular epithelium; the 
ingrowth being at one time apparently a forcible rush before 
which the loosened epithelium is driven. The ingrowth 
takes place in the first instance in the region of the base of 
the follicle.” 
Miss Lane-Claypon, in a paper lately communicated to the 
Physiological Society, “On the Post-Natal Formation of 
Primordial Ova,” states that the ovarian interstitial cells, and 
the follicular epithelial cells, like the primordial ova, are all 
“derived from the original ingrowths of the germinal epithe- 
cattle, as deduced from the study of 500 cases. The most usual length of 
this period appears to be twenty-one days, but the variation was found to 
range from six days to one hundred and twenty-one, or even more days. All 
variations between these periods were noted to occur. Schimidt’s observa- 
tions are in direct opposition to Beard’s speculation regarding the ‘ Span of 
Gestation and the Cause of Birth” (Jena, 1897), according to which the 
interval between two “heat ’’ periods is assumed to bear a fixed relation to 
the length of the gestation period. 
VoL. 49, parT 1.—NEW SERIES. 15 
