466 
ADAM SEDGWICK. 
Fig. 2. — Per. Balfouri. Unsegmented ovum with dark patch, but with- 
out central clear spot. 
Pig. 3. — Per. Balfouri. Unsegmented ovum with numerous dark patches, 
each with a clear centre. 
Pig. 4. — Per. Balfouri. Ovum with two segments from side. 
Pig. 5. — Per. Balfouri. Ovum with four segments from animal pole. 
Pig. 6. — Per. Balfouri. Side view of ovum with four segments. 
Fig. 7. — Per. Balfouri. Ovum with eight dark segments from animal 
pole. Greatest length ’4 to '48 mm. 
Pig. 8. — Per. capensis. Ovum fully segmented, with mosaic of ecto- 
derm cells and scattered branched endoderm cells. Greatest length (of egg- 
shell) - 56 to ’6 mm. 
Fig. 9. — Per. Balfouri. View of ovum from animal pole, as opaque 
object. 
Pig. 10. — Per. capensis. Aggregation of the endoderm cells beginning. 
Pigs. 11 and 12. — Per. Balfouri. Completion of same process. 
Pig. 13. — Per. capensis. Illustrates the same point. Length of ecto- 
derm patch - 32 to ‘4 mm. 
Pig. 14. — Per. capensis. Another phase of the same process. 
Pig. 15. — Per. capensis. Side view of ovum from preserved specimen. 
Cap of ectoderm cells covering half the endodermal mass. Progress of 
epibole. Diameter ’240 mm. 
Pig. 16. — Per. Balfouri. Stage in which the endoderm cells are 
covered by the (/.) latter ectoderm cells. Diameter \32 mm. 
Fig. 17. — Per. capensis. Side view of embryo. A few endoderm cells 
exposed. 
Pig. 18. — Ventral view of same. 
Pig. 19. — Per. capensis. Gastrula stage, ventral view. Blastopore 
distinctly circumseribed. Size '204 mm. X '240 mm. 
Pig. 20. — Side view of same in outline. 
Pig. 21. — Per. capensis. Gastrula stage, ventral view. Same stage as 
Fig. 19, but embryo slightly more elongated. 
Pig. 22. — Per. capensis. Stage A, showing slightly elongated blasto- 
pore with primitive streak at hind end. Greatest length *48 mm. a. Denotes 
the anterior end. 
