196 



OHAS. 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. 23fl5. — 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 Jl, 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, top view. Enlarged from a camera lucida sketch 

 of living egg. 



