DESCRIPTTON OF PLATES. 



Plate I. 

 Diagrams illustrating structure of Hydroida. 



1. Diagram of Hydra. 



2. Diagram of Hydroid colouy. 

 3,4, 5, Thread-cells. 



6. Medusa of Hydroid (after Hiiicks). 



7. Diagram of planula. 



For explanations of these diagrams, see chapter on 

 structure of the Hydroida, pp. 22 — 34. 



Plate II. 



1. Clava multicornis, enlarged (after Hincks), p. 36. 



2. Clava squamata, nat. size, p. 37. 



3. Turris neglecta, enlarged, p. 39. 



4. Cordylophora lacustris, hydranth enlarged. 4a, 



Nat. size, p. 40. 



5. Podocoryne carnea, enlarged, p. 42. 



Plate III. 



1. Lar Sabellarum, enlarged (after Gosse), p. 45. 



2. Coryne pusilla, nat. size, p. 46. 



3. Stauridium productum, enlarged (after Allman), 



p. 55. 



