344 KING. 



EXPLANATION OF PLATE XXVIIL 



All figures were drawn with the aid of the camera lucida. Plate XXXI is 

 reduced one-third. 



Fig. I. Vertical section through the black pole of a young ovarian egg, show- 

 ing the distribution of the yolk {Y) and pigment {PL) and the position of the 

 germinal vesicle (GV) just before the beginning of the hibernation period. Diam- 

 eter of the egg, I.I mm. Size of the germinal vesicle, 0.24 mm. x 0.36 mm. 

 Zeiss AA., Oc. 4. 



Fig. 2. A portion of the upper surface of a young ovarian egg, showing the 

 egg membranes. A and C, membranes belonging to the wall of the ovary ; ZR, 

 Zona radiata; P, perivitellin ; B, blood corpuscles. Zeiss apoc. 2 mm., Oc. 8. 



Fig. 3. Transverse section of the germinal vesicle in the same stage as that 

 of Fig. I, showing the position of the chromatin threads and the nucleoli. C, 

 chromatin threads ; Cy, fluid substance surrounding the lower part of the ger- 

 minal vesicle ; N, nucleoli. Zeiss D., Oc. 2. 



Fig. 4. Nucleoli from the germinal vesicle of an ovarian egg at the stage of 

 Fig. I. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 5. Chromatin threads from the germinal vesicle of an ovarian egg at the 

 stage of Fig. i. Zeiss apoc. 2 mm., Oc. 8. 



Fig. 6. Vertical section through the black pole of an ovarian egg, showing 

 the position of the germinal vesicle just before the beginning of its dissolution. 

 Diameter of the egg, i.i mm. Size of the germinal vesicle, 0.31 mm. x 0.39 mm. 

 Zeiss AA., Oc. 2. 



Fig. 7. The germinal vesicle of an ovarian egg at the beginning of its dissolu- 

 tion. LR, line of radiation ; A, granular substance below the line of radiation. 

 Zeiss D., Oc. 4. 



Fig. 8. Paired arrangement of the chromatin threads at the stage of Fig. 7. 

 Zeiss apoc. 2 mm., Oc. 8. 



Fig. 9. Youngest stage of the large nucleolar-like bodies found in the germi- 

 nal vesicle at the end of the hibernation period. Zeiss apoc. 2 mm., Oc. 4. 



Fig. id. Later stage of the same. Zeiss apoc. 2 mm., Oc. 4. 



Fig. II. Ordinary nucleolus found in the germinal vesicle at the end of the 

 hibernation period. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 12. Stages in the disintegration of the nucleoli during the dissolution of 

 the germinal vesicle. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 13. The lower pole of the germinal vesicle after the disappearance of the 

 nuclear membrane. LR, line of radiation from which fibers extend both above 

 and below; N, nucleoplasm breaking up into coarse granules; A, granular sub- 

 stance below the line of radiation. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 14. The lower pole of the germinal vesicle at a somewhat later stage 

 than that of Fig. 13. The line of radiation is composed of a dense lower part 

 sharply defined below, and an upper looser meshwork from which fibers extend up 

 between the granules of nucleoplasm. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 15. Beginning of a pronounced radiation extending from the line of 

 radiation. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 16. Filamentous chromosomes found in the germinal vesicle of the 

 youngest ovarian eggs obtained at the end of the hibernation period. Zeiss apoc. 

 2 mm., Oc. 8. 



