XI. 



EXPLANATION OF FIGUEES. 



PAGE. 



Fig. 1. An example of a small Hydroid colony 



(after Hincks) xvi. 



Fig. 2. An Athecate, or naked polypite . . 34 



Fig. 3. A Thecaphorean polypite provided with a 



horny covering, or receptacle . . . . 34 



Fig. 4. The structure of a typical Hydroid (Hydra) 

 and the distinctive difference between Budding 

 and Ova production ; also a dart cell (from 

 Parker and Haswell after Schneider) . . 36 



Fig. 5. Animal of Hydra vulgar is, showing young bud 



and mature bud ; also dart extruded from its cell 38 



Fig. 6. Diagram to show the nature of " budding " 40 



Fig. 7. Hydr actinia cchinata, showing " select" poly- 

 pite, reproductive buds, tentacular filaments and 

 horny spines. . . . . . . 42 



Fig. 8. Shows a small crustacean pierced by darts 



of a Hydroid . . . . . . 44 



Fig. 9. Shows a Thecaphore in which the receptacle 

 is produced into points, forming a roof or oper- 

 culum, over the polypite . . . . 46 



Fig. 10. Eeproductive bud with oral tentacles, of 



Tubularia coronata . . . . . . 50 



Fig. 1 1 . A typical Hydroid with its free Eeproductive 



bud, or Medusa . . . . . . 54 



Fig. 12. Transverse section of polipary of Coppinia 

 arcta for correlation with crust of Hydractinia 

 (fig. 7), and the section of stem of Antennularia 

 (fig. 13) .. .. .. 64 



Fig. 13. Transverse section of A ntennularia ramosa 75 



Fig. 14. A polypite of Plumularia pinnata expanded 

 and gorging a worm; also enlargements of 

 tentacle and dart cells in situ . . . . 78 



Fig. 15. A polypite of Plumularia pinnata retracted., 



with " Nematophores " or " Guard " polypites 79 



Fig. 16. Shows the change and atrophy which take 

 place in the " select" polypite in the course of 

 its evolution from the Athecate to the The- 

 caphorean form. Also the point where the fully 

 matured Medusoid fails to be set free 81 



