Plate II. 



In the figures contained in this plate, the sparingly dotted spaces 

 indicate the yolk-mass. The closely dotted parts in Figs. 52 and 53 are 

 sections of the equatorial zone overlaid by the recently differentiated epi- 

 blast, while in all other figures they represent both the hypoblast and 

 epiblast without discrimination. In Figs. 54-61, the parts of the epiblast, 

 which are marked with a double row of lines, show the thickening of that 

 layer around the blastopore and in the neural plate. 



All the figures drawn from the middle sagittal or the middle transverse 

 sections of the Bhacophorus eggs in their successive stages by the drawing 

 prism. Winkel Oc. 1 x Ob). 1. 



Y\g. 51. — Cross-section through the approximate center of an egg which 

 corresponds to about the stage represented in Fig. 20. 



Fig. 52. — Middle sagittal section of an egg which corresponds to the stage 

 represented in Figs. 9 and 23. 



Fi« - . 53. — Cross-section of another egg in the same developmental stage 

 as the above, through the approximate center but in a somewhat 

 oblique direction. The parts densely dotted in Figs. 52 and 53, are 

 the sections of the equatorial zone overlaid by the recently differ- 

 entiated epiblast. 



Fig. 54. — Middle sagittal section of an egg which corresponds to the stage 

 represented in Figs. 10 and 24-27, when the egg has not yet 

 begun its rotation. 



Figs. 55, 56. — Median sagittal and middle transverse sections of two different 

 eggs in a stage corresponding to that represented in Fig. 12 and 

 Figs. 28-30. 



Fig. 57, a, b. — Two median sagittal sections of two different eggs which 

 correspond to the stage represented in Figs. 13, 32 and 33. 



Fig. 58. — Sagittal section of another egg corresponding tu the stage re- 

 presented in Figs. 14, 36 and 37. 



Fig. 59. — Middle transverse section of another egg in the same stage. 



Figs. 60, 61. — Middle sagittal, and middle transverse, sections of the eggs 

 in a stage which is represented in Figs. 15 and 3S. 



