ON THE ANATOMY OF HISTlilOBDEF.LA HOMARI. 357 



Fig. 3. — Third and foiii'th nepliridiuni in the female. This and all 

 the subsequent fij^ures of the nephridia have been drawn from living 

 preparations impregnated with methyl-blue ; 12 mm. oil-immer., comp. 

 DCS. 4 and 6. x oOO and x 1000. 



Fig. 4. — Third nephridium in the male. 



Fig. 5. — Third nephridium in the male. 



Fig. B.^Second nephridium in the male. 



Fig. 7. — Male Histriobdella with claspers retracted, x 300. 



PLATE 18. 



Fig. 8. — Rupture of an egg through the Ijody-wall in a living prej)ara- 

 tion by compression of the cover-glass. The first maturation amphi- 

 aster is seen outside the body-wall in the sea- water, x 300. 



Fig. 9. — Male with claspers extended, x 300. 



Fig. 10. — Third and fourth nephridium in the male. X 800. 



Fig. 11. — Generative segment in the male. Taken from a living 

 preparation, showing the reproductive organs. 



Fig. 12. — Fourth nej)hridiuni in the male, x 800. 



Fig. 13. — Fourth nephridium in the male. Segment contracted. 

 X 800. 



Fig. 14. — Second nephridium in the female. X 800. 



PLATE 19. 



Fig. 15. — Reconstruction of the nervous system in the male, showing 

 the dorsal ciarve taken by the ventral nerve-cord in the region of the 

 penis. Lateral view, x 300. 



Fig. 16. — Young in egg-capsule. 



Fig. 17. — Young in egg-capsule. Earlier stage than that shown in 

 fig. 16. 



Fig. 18. — Oocyte with first maturation amphiaster. This, with the 

 subsequent figures, 19, 20, 26, and 32, are all drawn from the same egg- 

 cell. They show the changes of shape assumed by the egg in the move- 

 ments of the animal. They were drawn at intervals of from ten to 

 twenty minutes. 



Fig. 19. — Oocyte, same as that shown in fig. 18, drawn twenty minutes 

 later. 



Fig. 20. — Oocyte, same as that of fig. 19, fifteen minutes later. 



