55S PROCEEDINGS OF THE ACADEMY OF [DeC, 



Reference Letters. 



e., entoblasts 4d^-'-i and -id^-^-K nAb., nucleus of the cell 46. 



end., eudodenu. ph., pharynx. 



ey., eye. r., rhabdites. 



g., gangUon. y., yolk. 

 mes., mesoderm. 



Plate XXXV. — Fig. 1. — Living egg before fu-st maturation division, showing 



large germinal vesicle. 

 Fig. 2. — Living egg duiing the second maturation division, shomng amoeboid 



processes. 

 Fig. 3. — Living egg after second maturation division. 

 Fig. 4. — Living egg during the first division. The cell C-D is slightly larger 



"than A-B. 

 Fig. 5. — Stained egg in the second division. From left side, showing the 



crossing of the spindles. 

 Fig. 6. — Living egg in the four-cell stage, from the animal pole. 

 Fig. 7. — Formation of the first quartet. From right side, showing dexio- 



tropic cleavage. 

 Fig. 8. — Living egg in the eight-cell stage. From animal pole. 

 Plate XXXVI. — Fig. 9. — Lseotropic division of the preceding eight cells. The 



spindles in the D quadrant show an advance over the others. From 



the animal pole. 

 Fig. 10. — Living egg with sixteen cells. From the animal pole. 

 Fig. 11. — Same as fig. 10, but from vegetative pole. 

 Fig. 12. — Dexiotropic divisions of cells la^-ld' and of 2a-2d. From animal 



pole. 

 Fig. 13. — Thirty-two cells. Dexiotropic divisions of la^-'-ld^-^ From 



animal pole. 

 Fig. 14. — Thirty-two cells, showing dexiotropic formation of 3a and 3c. 



Vegetative pole. 

 Fig. 15. — Thirty-two cells from vegetative pole, shoTving spindles for forma- 

 tion of 46 and 4d. 

 Plate XXXVII. — Fig. 16. — Same as Fig. 15, from right side. 



Fig. 17. — Thirty-six cells from near vegetative pole. Spindle in 2c^ 2a^ 



and 2(P have divided. 

 Fig. 18. — Thirty-nine cells. From animal pole, showang lseotropic forma- 

 tion of apical cells. 

 Fig. 19. — Forty-five cells, from the right posterior side. Shows the first 



division of the mesentoblast 4d. 2d^ also dividing. 

 Fig. 20. — Forty-seven cells. From vegetative pole. 

 Fig. 21. — About the same stage as fig. 20,draT\Ti from the right side, shows 



the unequal di\asion of 2c' and 2bK Also spindles in Ic^-' and W-^. 



la'-^-ld^'^ have divided dexiotropically (see fig. 22). 

 Plate XXXVIII. — Fig. 22. — Slightly older egg than fig. 21, dra-^Ti from left 



upper side. Shows division of la'-'-^-ld'-'-^ and of 1¥-'^. la'-^ and 1¥'^ 



have divided previously. Also shows losotropic di^ision of la^-'-ld^'. 

 Fig. 23.— Still older egg, sho\\ang the same division as fig. 22, but more 



advanced. From animal pole. 

 Fig. 24. — Egg from animal pole, showing preceding diAdsions completed and 



dexiotropic division of Id''-''. Also the bilateral division of 4d^ 

 Fig. 25. — Similar stage from vegetative pole. Shows spindle for bilateral 



division of 4d^ Also lseotropic division of 2a^'-2d^^ 3d preparing to 



di^^de. 

 Fig. 26. — Shows division of 4d^ completed and spindle in 4d'. Also shows 



di\asion of 2d^ and 2b^, of 3d and 3b, and of 2a^-\ 

 Fig. 27. — Similar stage from the left side. Shows division of 2a^-*, 4d' and 



2b--''; also of la^-^-K 

 Plate XXXIX. — Fig. 28.— Egg from animal pole, showing di^^sions of la'-'-^'- 



Id'-'-^-^; also of la'-^-i and Ic'-'-K 



