NUMBER OF OVA: ALBINO RAT A409 
ovary. The nuclei which were counted were those most dis- 
tinctly stained by hematoxylin. The diameter of the nuclei of 
the ova range from 8 to 12 » both in the primitive ova and in the 
definitive ova. By this method we might make a double count- 
ing occasionally, because it is based on the counting of the dis- 
tinctly stained nuclei. On the other hand, there is no fear of 
missing ova, because the sections were 10 » thick, while the 
smallest nucleus has a diameter of 8 » at least. 
For counting the number of ova in younger ovaries, especially 
those before twenty days of age, the use of the net-micrometer 
is necessary. For the measurement of the diameter of the larger 
ova a Zeiss compens. ocular no. 6 and object. 4 was used and 
the micrometer eyepiece was so adjusted that each division 
equalled 4 ». I have divided all the ova, according to their 
diameters, into four groups: 
Group Diameter 
See eee te alge: Ti Ee a. atc ec teeta less than 20u 
UDOT REE AS cote shed tee RO SP Aes id cos (ac oe a 7 20 to 40u 
UOT) bests Ss a Se aed ine ho tre RS SLO Sl i a 40 to 60u 
Vidic ccc OCR Da ieee OC ETC RE IRE es ro oto con Ree over 60u 
We find ova, especially in the mature ovaries, which show sev- 
eral stages of degeneration. ‘These stages I have divided into 
four groups. 
A. The follicles are poorly developed and have one to three 
layers of cells. In the centrum the ovum is not found, but in- 
stead there is a homogeneous hyalin mass which stains red with 
eosin. 
B. The follicles which belong to this group show merely the 
outline of the ova in follicles, but the ovum is without a nucleus. 
Such ova stain red with eosin but faintly. 
C. In this group the follicles are well developed, and some- 
times are almost like the mature follicles, having many layers of 
follicle cells, but these cells are either already degenerated or 
are about to degenerate. In these follicles the large cavity usu- 
ally contains fluid or sometimes a colloidal mass which stains a 
deep red with eosin. However, no ova can be found. The 
shape of the follicles is either circular or oval. 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 27, NO. 4 
