Plate 4. 



Embryonic Development and Larval Stages. 



Figs. 1 — 16 and IS refer to Pdtogaster cwrmtus, Figs. 17, 19 and 20 to Sacculina neglecta. 



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

 1st antenna. 2nd A 2nd antenna, eh chitinous investment of Kentiogon. E Endoderm cells. Em Embryonic 

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

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

 res vesicle representing antennal gland. VP ventral plate. 



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



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



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



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



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



Fig. 0. Formation of blastoderm, later stage. Whole preparation. X 650. 



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



Fig. S. 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 plate and first two appendages. X 650. 



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



Fig. 17. Free swimming Nauplius of Sacculina neglecta. Ventral view. X 175. 



Fig. IS. Free swimming Nauplius of Peltogaster curvatus. Ventral view. X 175. 



Fig. 19. Free swimming Cypris of Sacculina neglecta. Lateral view, x 350. 



Fig. 20. Horizontal section through fixed Cypris of Sacculina neglecta. X 325. 



