196 CHAS. B. WILSON. 



Tig. 21.— Transverse section of a regenerating papilla very near its 

 posterior end, showing ventral grooves and beginning of the lateral nerve- 

 cords. 1 and 3. 



Fig. 22.— Same farther forward, showing lateral nerve-cords migrating 

 toward their normal position. 



Fig. 23.— Same still farther forward ; nerve-cords nearly in their normal 

 position, and circular muscles well developed. 



PLATE 10. 



Fig. 23«.— Fertilised egg, showing flattening of the superior pole previous 

 to the giving off of the polar bodies. 1 and 7. 



Figs. 24 — 36. — Maturation of the egg and formation of the polar bodies, 

 with the beginning of filose activities. 1 and 7, tube drawn 60 mm. These 

 drawings are all from the same egg, and were taken at the following intervals: — 



11.05 a.m., 11.065, 11.08, 11.21, 11.216, 11.22, 11.228, 11.235, 11.24, 

 11.27, 11.28, 11.335, and 11.40. 



Fig. 37. — A second egg, showing abnormal activities during completion of 

 the polar bodies. 1 and 7 ; tube drawn 60 mm. 



Fig. 38. — A third egg with unequal papillae and slightly abnormal activities. 

 Magnification the same. 



Fig. 39. — Egg with polar bodies pressing against the inner membrane and 

 bulging it outward. 1 and 7 ; tube drawn 60 mm. 



Fig. 40. — Polar bodies of egg shown in Figs. 24 — 36, taken at 11.36. 

 3 and 7 ; tube drawn 60 mm. 



Fig. 41. — Same, first polar body at 11.17. 



Fig. 42. — Polar bodies and sperm at beginning of first segmentation. 

 3 and 7. 



Fig. 43. — Same at close of first segmentation. 



Fig. 44. — Polar bodies during 64-cell stage. 3 and 7 ; tube drawn 60 mm. 



Fig. 45. — Same in 128-cell stage. 



Figs. 46 — 50. — First segmentation, showing filose activities of polar bodies 

 and blastomeres. All figures from the same egg at the following intervals : — 



12.06 m., 12.065, 12.09, 12.11, 12.16. 1 and 7 ; tube drawn 60 mm. 



Fig. 51. — Egg in which blastomeres were almost entirely separated, and 

 in which they showed perceptible motion during flattening. Same magnifica- 

 tion. 



Fig. 52. — Same egg as in Figs. 46 — 50, in the 4-cell stage (12.30). Central 

 opening crossed by spin-threads. 



Fig. 53. — Four-cell stage, toj) view. Enlarged from a camera lucida sketch 

 of living egg. 



