37O LEON AUGUSTUS HAUSMAN. 



EXPLANATION OF PLATE I. 



FIG. i. A fully expanded, mature Sagartia with its tentacles in exploring 

 posture, after having been stimulated with beef juice injected into the water. The 

 object to which it is attached is an edible or black mussel (Mytilus edulis). 



FIG. 2. Contracted mature Sagartia. 



FIG. 3. Transection through a typical ideal tidal pool, to show the disposition 

 of Sagartia individuals, and their general ecological relationships. 



1. Sagartia lucirp. 



2. Edible or Black Mussel (Mylilus edulis). 



3. Ribbed Mussel (Modiola plicatula). 



4. Mud Flat or Elephant Snail (Nassa obsoleta). 



5. Oyster Drill (Urosalpinx cinerea). 



6. Periwinkle (Littorina littoria), not numbered in the figure. It occurs in 



great numbers, everywhere. 



7. Oyster (Ostrea mrginica) rare in tidal pools. 



8. Clam Worms (Nereis), in mud among masses of mussels. 



9. Small Ribbon Worms (Mechelia) . 



10. Starfish (Asterias forbesi and vulgaris). 



11. Hermit Crabs (Eupagurns longicarptis). 



12. Mud Crabs (Panopcus herbestii and others). 



13. Rock Barnacle (Balanus balanoides)^ 



14. Green Beach Flea (Orchestia agilis). 



FIG. 4. Sagartia, capturing a small Beach Flea (Orchestia agilis). 



FIG. 5. Partially contracted Sargtia, of large size, just before fission. A strong 

 light had been placed behind the creature, revealing the manner of the accommo- 

 dation of the contracted tentacle blossom, and the folded sides of the gastrovascular 

 cavity. The latter is seen to be empty of food. 



