24 ARTHtJR DENDY. 



showing syncytium and nuclei. Drawn under Zeiss objective F, oc. 2, camera 

 outlines. 



'Fig. 15. — Part of a transverse section of a tentacle from the float. Drawn 

 under Zeiss objective D, oc. 3, camera outlines, 



Tig. 16. — Part of the ectoderm layer from a section similar to the last. 

 Drawn under Zeiss objective F, oc. 2, camera outlines. 



Fig. 17. — Two thread-cells with their cnidoblasts and cuidopods, from one 

 of the tentacles of the float. Drawn under Zeiss objective F, oc. 2. 



(In Figs. 18 — 21 inclusive, showing stages in the development of the 

 medusse, the histology is, for the sake of clearness, rendered diagrammatic- 

 ally ; tlie endoderm is shaded ; the external ectoderm is unshaded, and the 

 ectoderm of the endocodon and its derivatives is unshaded but has the nuclei 

 represented by dots. All are drawn, with the aid of the camera lucida, under 

 Zeiss objective D, oc. 2.) 



Fig. 18. — Two young medusa buds seen in longitudinal section, — B before 

 the formation of the endocodon; C with the endocodon and manubrium 

 developing. (Owing to slight obliquity of the sections, the cavity of the 

 stolon is not shown.) 



Fig. 19. — Slightly older medusa bud in longitudinal section. 



Fig. 20. — Still older medusa bud in longitudinal section, with a very young 

 bud also springing from the same stolon at A. 



Fig. 21. — Transverse section of a medusa bud a little older thau the last, 

 showing the radial canals, etc. 



Fig. 22.— Side view of one of the oldest medusae found. Drawn from 

 spirit specimen under Zeiss objective A, oc. 1, as a transparent object. 



Fig. 23. — Oral view of similar specimen under similar conditions. The 

 mouth of the bell is now visible in the middle of the velum, between the four 

 tentacle-bearing arms. 



Fig. 2i. — Aboral view of similar specimen under similar conditions, 

 showing the four radial canals, subumbrellar musculature, etc. 



Fie. 25. — Transverse section of a medusa of about the same age. Drawn 

 under Zeiss objective A, oc. 3, camera outlines. 



Note.— The microscopical sections were all stained with borax carmine. 



