640 Gro. W. TANNREUTHER, 
Fig. 24. Later stage than preceding, showing granular appearance 
of the polar bodies and pro-nucleus, just before the breaking down of the 
wall of the germinal vesicle. pr» pronucleus, 7. s yolk spheres. 
Fig. 25. Long. section of ovum showing the fusion of the nucleo- 
plasm with the periplasm. pbs polar bodies, prn pronucleus. 
Fig. 26. ‘Tangential section a little later than preceding, showing 
the spreading of the nucleoplasm. prn pronucleus, ph, second polar body, 
pr periplasm. 
Fig. 27. Condition of ovum with polar bodies scarcely visible and 
the pronucleus moving toward the interior of egg. 
Fig. 28. Pronucleus in center of the ovum. 
Plate 50. 
Fig. 29. Long. section of follicle of a half-grown embryo. e. ch end 
chamber, o. gl ovarian glands, ov ova, n. s nutritive string. 
Fig. 30. Section of follicle at time of birth, showing last ovogonial 
division. ovg ovogonia; lettering same as preceding. 
Fig. 31. Transverse section of follicular epithelium at base of end 
chamber, showing an ovum during growth, and the origin of the true ova 
from the follicular cells. oog ovogonia, f. e follicular epithelium. 
Fig. 32. Condition of follicle at the beginning of deposition, showing 
the exact relation of the ovarian glands, nutritive string and ovum. ov ovum. 
Fig. 33. Section of follicle a little later than preceding, containing 
a completely formed ovum and showing the condition of the ovarian glands 
near the end of deposition. 
Fig. 34—40. Cleavage and formation of the blastoderm in the asexua 
forms. pl polar body, clv cleavage nuclei, bl blastoderm. 
Fig. 41. Long. section of egg with completely formed blastoderm, 
at the beginning of invagination. Invagination first begins by proliferation 
of cells at posterior pole. pe proliferating cells of blastoderm, pr. y pri- 
mary yolk, el end ligament. 
Fig. 42. Section a little older than preceding showing entrance of 
secondary yolk into the interior. s. y secondary yolk. 
Fig. 43. Long. section of a single follicle of asexual female. e./ end 
ligament, o. gl ovarian glands, ov ovum. 
Fig. 44. Transverse section of a single cyst showing the prophase 
of the spermatocyte of the first order. 
Plate ble 
Fig. 45. Long. section of a single lobe of the testis, showing the 
male cells in different stages of development. « anterior end, p posterior, 
sp, spermatocytes of first order, sp, spermatocytes of second order. 
