344 The Oogonosis of the Tortoise 



Fig. 51. Section of an egg showing a cytocenter similar to the preceding 

 as regards the number of circles or zones, but in which the reticulum of 

 the outer zone is more distinct; also yolk-nuclei in the cytoccel or outer limit 

 of the cytocenter. 



PLATE III. 



Fig. 52. Section of an egg at right angle to egg axis, showing the cyto- 

 center consisting of a dark central body surrounded by a light ring which 

 again is surrounded by a system of radial fibers like an aster; a number of 

 yolk-nuclei in the cytoplasm. 



Fig. 53. Section of egg showing the zones of the cytoplasm, the subcutic- 

 ular, peripheral, the cytoccel and finally the zones of the cytocenter; yolk- 

 nuclei in the cytoplasm. 



Fig. 54. Section of an egg showing germinal vesicle with peripheral nu- 

 cleoli, some of which are vacuolated; and besides the bead-like nuclear retic- 

 ulum; a fibrous cytocenter resembling an aster; one large, round yolk-nucleus, 

 and two smaller ones. 



Fig. 55. Section of egg at right angles to the egg axis showing central 

 body, cytocenter and the cytoplasmic zones around it. 



Fig. 56. Section showing cytocenter in the form of an aster and a central 

 body, centrosome and surrounding granular zone; a germinal vesicle showing 

 peripheral nucleoli and chromatin bodies arranged in rows. 



Figs. 57, 58, 59, 60, 61. Serial sections of the same egg, at right angles 

 to the egg axis, showing (a) yolk-nuclei near the germinal vesicle; still more 

 of them in (b) where the section passes through the center of the germinal 

 vesicle, yet more in (c) where many of them are gi*ouped around the pole 

 of the germinal vesicle next to the cytocenter; the aster-like cytocenter in 

 (d) surrounded by numerous yolk-nuclei; the central sphere (e) with radial 

 fibres on one side and numerous yolk-nuclei arranged in a circle around it. 



Fig. 62. Section of an egg, showing germinal vesicle, peripheral nucleoli, 

 nuclear network, and a cytocenter consisting of a network of deliate fibres. 



Fig. 63. Section showing germinal vesicle, with peripheral nucleoli, and 

 bead-like chromosomes imbedded in a somewhat granular karyolymph or 

 nuclear matrix. A large spherical cytocenter with distinct astral rays evi- 

 dently continuous on one side with the cytoreticulum, at the periphery a 

 large yolk-nucleus. 



Fig. 64. Section of an egg showing germinal vesicle; cytocenter with 

 archoplasmic zone and astral rays in the cytoplasm and numerous yolk-nuclei 

 in the peripheral zone of the cytoplasm. 



Fig. 65. Section of egg showing germinal vesicle and cytocenter; section 

 not parallel with egg axis; cytocenter and germinal vesicle in different sec- 

 tions hence the closeness of one to the other. The cytocenter appears dia- 

 grammatic, but a true representation of very many of these centers, the large 

 microsomes being slightly exaggerated. 



PLATE IV. 



Fig. 66. Section of an egg showing a single large vitelline-body of homo- 

 geneous substance resembling archoplasm occupying a somewhat eccentric 

 position in the cytoplasm and staining very similarly to*" the granular matrix 

 of the germinal vesicle. 



