482 TREADWELL. 



EXPLANATION OF PLATE XXXVIIL 



Fig. 25. Completed division of second quartette in quadrant B. 



Fig. 26. Completed division of second quartette in quadrant D, showing 

 X1.2. Bilateral division of 4d, 3C2, 3d2. 



Fig. 27. Bilateral division of 4d, etc., from below. 



Fig. 28. Third division of second quartette cell and first division of 3a2 

 and 3b2. 



Fig. 29. Side view of preceding stage, showing A quadrant. 



Fig. 30. Same as 29, showing D quadrant. 



Figs. 31 and 32. Division of X3. 



Figs. 33 and 34. Formation of fifth group of micromeres. 



Fig. 35. Division of X1.2 and 3C2.1. Note the small superficial i rea of 4a, 

 4b, and 4c. 



Fig. 36. First division of 4a, 4b, and 4c. 



