Piate 4. 



Embryonic Development and Larvai Stages. 



Figs. 1 — 16 and 18 refer to Péltogaster curvatus, Figs. 17, 19 and 20 to Saeculina negleeta. 



Ab abdomen. Ant Antenna of Cypris. 1, 2, 3 lst, 2nd and 3rd segments of Nauplius. IstA 

 lst antenna. 2ndA 2nd antenna, eh chitinous investment of Kentrogon. E Endoderm cells. Em Embiyonic 

 cells. Ect Ectoderm. Eh frontal horns. G glands of Cypris. h chitinous tendons of Cypiis. md man- 

 dible. muse muscles. t tentacles. th.app thoracic appendages. Th thoracic rudiment. sk skeletal support. 

 ves vesicle representing antennal gland. VP ventral piate. 



Fig. 1. Two celi stage. Whole preparation side view. X 140. 



Fig. 2. Two celi stage. Horizontal section through upper pole. 650. 



Fig. 3. Four celi stage. Whole preparation viewed from lower pole. X 140. 



Fig. 4. Four celi stage. Horizontal section through upper pole. X 650. 



Fig. 5. Formation of blastoderm. Longitudinal section. X 650. 



Fig. 6. Formation of blastoderm, later stage. Whole preparation. X 650. 



Fig. 7. Gastrulation. Optical section. X 650. 



Fig. 8. Gastrulation. Optical section, later stage. X 650. 



Fig. 9. End of Gastrulation, breaking up of archenteron. Optical section. X 650. 



Fig. 10. Segmentation of lateral germ bands. Whole preparation. Dorsal view. X 650. 



Fig. 11. Segmentation of lateral germ bands. Horizontal section. X 650. 



Fig. 12. Formation of Nauplius. Lateral view, whole preparation. X 650. 



Fig. 13. Formation of Nauplius. Ventral view, whole preparation. X 650. 



Fig. 14. Horizontal section through 13. X 650. 



Fig. 15. Transverse section through 13, cutting ventral piate and first two appendages. X 650. 



Fig. 16. Transverse section through 13, anterior to 15. X 650. 



Fig. 17. Free swimming Nauplius of Saeculina negleeta. Ventral view. X 175. 



Fig. 18. Free swimming Nauplius of Péltogaster curvatus. Ventral view. X 175. 



Fig. 19. Free swimming Cypris of Saeculina negleeta. Lateral view. X 350. 



Fig. 20. Horizontal section through fixed Cypris of Saeculina negleeta. X 325. 



