Explanation of Letters in the Figures. 



A. C.=Archenteron cavity. 



E. = Equatorial line. 



S. C. = Segmentation cavity. 



V. = Vertical axis of the rotating eggs. 



V = Original vertical axis of eggs. 



'Oft' 



Plate I. 



Fig?. 1-19. Developmental stages of the Bhacophorus egg, 

 magnified about 11 or 12 times. 

 Figs. 1-6. — Segmentation up to the fourth cleavage stage. 



In Fig. 2, the second cleavage-plane should have been marked 



II instead of IV, which is an error. 

 Fig. 7. — Side view of an egg, 7-10 hours after deposition. 

 Fig. 8. — Side view of an egg, 10-15 hours after deposition, when the first 



dorsal lip of the blastopore has not yet appeared. 

 Fig. 9. — Posterior view of an egg, 20-25 hours after deposition, with the 



dorsal lip just appeared, and with the fully grown upper area of the 



segmentation cavity which had already begun to appear in the last stage. 

 Fig. 10. — Posterior view of an egg, 35-45 hours after deposition, with the 



broadly spread equatorial zone interposed between the blastopore lip, 



which has just completed its encircling, and the tolerably reduced 



area of the segmentation cavity. 

 Fig. 11. — Posterior view of another egg, 40-50 hours after deposition, still 



standing vertically upon the middle point of the blastopore area. 

 Fig. 12. — Posterior view of another egg } 45-55 hours after deposition, with 



the faintly visible outline, of the neural plate. 

 Fig. 13. — Left side view of a much advanced egg, 50-60 hours after 



deposition, when the egg has rotated considerably and the blastopore 



and the area of the segmentation cavity placed opposite each other 



have been greatly reduced in nearly equal ratio. 

 Fig. 14. — Left side view of an egg, 5^>-G~) hours after deposition, when the 



blastopore was completely closed and the axial region of the embryonic 



body may be well recognised by the presence of the deep neural 



groove as well as the slightly raised neural folds. 

 Fig. 15. — Left side view of another egg, 60-70 hours after deposition, when 



the neural groove has just closed. The embryo body is flattened 



out over the surface of the yolk mass. 

 Fig. 16. — Left side view of a much advanced egg, 70-90 hours after 



