238 N. M. STEVENS, 
Explanation of Plates. 
Plates 20—21. 
The figures were all drawn with camera from sections of material 
fixed with sublimate acetic, cut 5—7 u thick, and stained on the slide 
by the HEIDENHAIN iron-haematoxylin method. 
Plate 20. 
Fig. 1. Cross-section of a young ovary, showing very young oocytes 
at the center, and somewhat older ones (a—e) with accessory cells. 
a shows a surface view of the reticular network in the nuclear mem- 
brane. Banch & Lomp, objective 1/,, ocular C. 
Fig. 2. Cross-section of an ovary containing nearly ripe oocytes 
(b) with very small chromosomes, cast out granules, thick egg-membrane, 
and accessory cells with tubular opening for the entrance of the 
spermatozoon. a is an oocyte with somewhat reduced chromosomes, 
yolk globules at the periphery, and membrane thickened slightly on 
the median side. B. & L., obj. "Jo, oc. C. 
Fig. 3. Three epithelium cells (a) from the region of youngest 
oocytes, and two cells (b) lateral to that region. B. & L., obj. 4/,., 
oc. C. 
Figs. 4—8. Young oocytes from the central region of the ovary. 
IB. eels ob). 2,5, 0c.2C. 
Fig. 9. Young oocyte with one accessory cell attached and chromo- 
somes showing short side branching. B. & L., obj. 1/,,, oc. ©. 
Fig. 10. Section of an oocyte somewhat younger than Fig. 2a, 
with much branched chromosomes, and large yolk globules at the peri- 
phery. B. & D 10h ye soe: 
Fig. 11. Section of a nucleus from an oocyte in the same stage 
as Fig. 2b, showing three short chromosomes, a large number of cast 
out granules, and the adjacent nuclear-membrane very thin. B. & L., 
ODIs ue rac, °C. 
Fig. 12. Section of a nucleus in a somewhat earlier stage than 
hat of Fig. 11, showing a longer chromosome with granules attached, 
