CARPENTER. — FEEDING REACTIONS OF THE ROSE CORAL. 161 



heavily loaded with nematocysts. When the end of a tentacle is 

 chemically stimulated with meat extract, the retractor muscles of the 

 polyp contract. 



4. Carmine grains dropped on the oral surface of an expanded polyp 

 are transferred by ciliary action to the periphery. When the particles 

 of carmine have previously been soaked in meat juice, the cilia usually 

 continue to beat in an outward direction ; occasionally, however, they 

 reverse their effective strokes. The chief function of the cilia seems 

 to be that of keeping the oral surface clean. 



5. When plankton is fed to a polyp the small organisms are affixed 

 by the tentacles, the oral disk sinks, and the marginal zone folds in- 

 ward until it completely roofs over the tentacles and the depressed 

 oral disk. Into the superficial chamber thus formed, the stomodaeum 

 and mesenterial filaments project, and here the mesenterial filaments, 

 which are the digestive organs of the polyp, probably digest and ingest 

 or absorb the captured plankton, little of which appears to find its way 

 into the reduced gastro-coelomic cavity. Extra-coelenteric digestion 

 apparently takes place, therefore, in rose-coral polyps. 



6. There is experimental evidence of the transmission of impulses 

 of at least a nervoid character from ectodermal receptor cells through 

 the mesogloea to endodermal effectors (muscles). This transmission is 

 not confined to a single polyp, but may pass from one polyp to another. 



7. It is known that branching cells (so-called "connective-tissue 

 cells ") occur in the mesogloea of Isophyllia. These extend fi-om the 

 ectoderm to the endoderm, and so have the topographical relations of 

 adjustor cells, placing the receptor in communication with the effector. 

 In the absence of exact information as to the origin, mutual relation- 

 ships, and functions of these cells, it is nevertheless suggested that 

 future studies may show them to be primitive synaptic neurones. 



Bibliography. 

 Carlgren, 0. 



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 port bei den Actiniarien und Madreporarien. Biol. Centralbl., Bd. 

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 Duerden, J. E. 



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 Duerden, J. E., and Ayres, S. A. 



:05. The Nerve-layer in the Coral Coenopsammia. Seventh Report 

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