214 CON KLIN, 



EXPLANATION OF PLATE III. 



Fig. 25. Dexio tropic division of the mesentoblast, 4D. The cell 3d is dividing 

 almost radially. Tvsfenty-nine cells. 



Fig. 26. Separation of 4D into right and left halves. Radial division of 3c 

 and 3b (3a divides a little later). Dexiotropic division of 2a', 2b', 2C', 2d' and 

 formation of tip cells of cross (2di-i, 2ci-', etc.). 



Fig. 27. Same egg seen from the posterior side, showing position of right and 

 left mesentoblasts and direction of spindles in some of the outer belt cells. 



Fig. 28. Same egg seen from right side, showing direction of spindles in outer 

 belt cells. 



Fig. 29. " Resting stage " after the divisions shown in preceding figures. The 

 cross is shown here and elsewhere in heavier outline. Forty-two cells, 4 apicals, 8 

 cross, 4 turrrets, 20 belt cells, 2 mesentoblasts, 4 macromeres. 



Fig. 30. Bilateral division of mesentoblasts. 



Fig. 31. Completion of cleavage shown in preceding figure and formation of 

 enteroblasts, E' and E^. Dexiotropic division of basal cells of cross, la'-^ ib^-° 

 (ic''- divides a little later). Forty-four cells. 



Fig. 32. Completion of division of basal cells in arms a, b, and c, and forma- 

 tion of middle cells, la'-^-^ ib'-^-^ ic^-^-^ Second bilateral division of mesento- 

 blasts. Forty-seven cells. 



Fig. 33. Completion of division of mesentoblasts shown in preceding figure 

 and formation of the primary mesoblast cells m' and m^. Laeotropic division of 

 the macromeres A, B, and C and formation of the remaining members of the fourth 

 quartette, 4A, 4B, 4C. Laeotropic rotation of whole ectoblastic plate. Fifty-two 

 cells. 



Fig. 34. Side view of same egg, showing laeotropic formation of fourth quar- 

 tette. Cf. Fig. 24. 



Fig. 35. Division of 2c'--, 2c^'', 2b''^ 2b^'' (aa'-^ and 2a*'' divide immediately 

 after). Flattening of cells 4A, 4B, 4C into furrows between macromeres. 



Fig. 36. Completion of divisions shown in preceding figure. Bilateral cleavage 

 of 3c' and 3di (3a' and 3b' divide later, see Fig. 38). Sixty cells. 



