THE PYCNOGONIDS. 73 



Fig. 15. Eyes of same. 



Fig. 16. Ventral organs of same. Early stage of third pair of 

 ganglia. 



Plate II.— Sections of Pallene empusa. 



Fig. 17. Longitudinal section through stomodaeum of young 

 embryo. First origin of mesoblast at M. 



Fig. 18. Cross-section through stomodaeum of older stage. See 

 line 18, Fig. I, Plate IV. 



Fig. 19. Section anterior to last. See line 19, Fig. I, Plate IV. 



Fig. 20. Section anterior to Fig. 19. See line 20, Fig. I, Plate IV. 



Fig. 21. Cross-section of ventral organs. See line 21, Fig. I, 

 Plate IV. 



Fig. 22. Cross-section of ventral organs at stage III. 



Fig. 23. Cross-section of ventral organs at stage V. 



Fig. 24. Cross-section of ventral organs at stage VI. 



Fig. 25. Cross-section of embryo at stage III. 



Fig. 26. Cross-section through brain and second pair of ventral 

 ganglia of stage III. 



Fig. 27. Cross-section of embryo in the plane of a pair of legs, 

 about stage VI. 



Fig. 28. Cross-section of embryo in the plane between a pair of 

 walking legs, about stage VI. 



Fig. 29. Cross-section through the rudimentary abdomen and 

 the body of an embryo, stages VII-VIII. 



Plate III. 



A-J, Pallene empusa. a-c, Phoxichilidium maxillare. d-f, Tany- 



stylum orbiculare. 



Fig. A. Segmenting egg, side view, 2-celled stage. 



Fig. B. Segmenting egg, seen from above, 4-celled stage. 



Fig. C. Segmenting egg, seen from above, 8-celled stage. 



Fig. D. Segmenting egg, seen from below, 8-celled stage. 



Fig. E. Segmenting egg, side view, 16-celled stage. 



Fig. F. Segmenting egg, surface views of micromeres, 16-celled 

 stage. 



Fig. Gr. Segmenting egg, side view, 16 macromeres, 8 micro- 

 meres. 



Fig. H. Segmenting egg, side view, 24 macromeres, 16 micro- 

 meres. 



Fig. J. Segmented egg, lower pole, base of pyramidal cells shows 

 at surface. 



