2l6 CONK LIN. 



EXPLANATION OF PLATE IV. 



Fig. 37. Anterior view of egg shown in Fig. 36. 



Fig. 38. Dexiotropic division of 3a' and 3b'. Division of 2d'-^ and 2d^-' (the 

 corresponding divisions in the other quadrants are shown in Fig. 36). Sixty-four 

 cells. 



Fig. 39. Posterior view of same egg. 



Fig. 40. Anterior view of another egg of nearly the same stage, showing 

 division of 3b'. 



Fig. 41. Third bilateral division of mesentoblasts. Belated division of 2a''-'. 



Fig. 42. Complete separation of mesoblast and entoblast. Formation of en- 

 teroblasts, e' and e% and of mesoblastic teloblasts, M^ and M^ Division of 

 primary mesoblast cells, m' and m^. Transverse division of the middle cells in 

 the right, left, and anterior arms of the cross ; teloblastic division of the basal and 

 terminal cells of the posterior arm. Division of 3b^ a little before the correspond- 

 ing cells in the other quadrants. Sixty-eight cells. 



Fig. 43. Anterior view of another egg of similar stage, showing the division 

 of 3b^ and 3C^. 



Fig. 44. " Rosette division " of the apical cells. Transverse division of the 

 tip cells in arms a, b, and c. The cell 3c'-^ is dividing, 3d'-'^ has divided. Eighty 

 to eighty-six cells. 



Fig. 45. Same egg seen from the posterior side. 



Fig. 46. Transverse division of the basal cells in the arms a, b, and c. Nearly 

 horizontal division of 2a°-'-', 2a^-'-^ 2b^'''', 2b^-'-^, etc. Laeotropic division of 

 2a'-^-', 2b'-^-', etc. Dexiotropic division of 3bi-i, laeotropic division of 3b'-^ (the 

 corresponding cells in the quadrant A divide soon after, 3c'-^ and 3d'-^ have 

 already divided, 3c'-' and 3di-' do not divide). One hundred and nine cells, 

 — 4 apicals, 4 rosette, 4 turrets, 22 cross cells, 58 outer belt cells, 6 mesoblasts, 4 

 enteroblasts, 7 entoblasts. 



Fig. 47. Same egg seen from anterior side, showing direction of spindles in 

 outer belt cells. 



Fig. 48. Posterior view of slightly older stage, showing teloblastic divisions of 

 posterior tip cells (2di-'-' and 2d'-'-^) and other cells of the same group (2d). 



