TUBULAEIA. 65 



Faint whirls, almost inconspicuous in the living product, indent the origin 

 of the branch and the ea-tremitij of the twigs. Chestnut brown or umber 

 is the predominant colour of the inorganic parts ; the hydra, very minute, 

 is reddish. — Plate XI. fig. 2, enlarged. 



As the extremities of this product consist of hollow cylinders, with- 

 out any cellular enlargement, the hydra retreats simply within for protec- 

 tion. "When rising, it is protruded by a very long flexible body or neck, 

 capable of great recurvature, which is bordered by from 6 to 14 muricate 

 tentacula, environing an obtuse central cone — the stomach. The tenta- 

 cula are susceptible of much elongation, when they become almost of 

 cylindrical form. The stomach is indicated by a rough dark line de- 

 scending far within the body. — Fig. 3. 



Although the hydra protruded from the extremity of a cylinder, some 

 issued immediately from the side of the stalks, without the obvious inter- 

 vention of a tubular twig. 



The great flexibility of the neck induced me to consider this product 

 as allied to the Coryna, on obtaining a smaller specimen many years ante- 

 cedent to those now described ; nor even now do I speak positively of the 

 name and species. It is susceptible of complete recurvature, or of look- 

 ing behind, as we should express of other animals. 



Naturalists have affirmed that a circulating fluid subsists in the Ttibii- 

 laria indivisa, a zoophyte of considerable magnitude, and of which the or- 

 ganic portion exceeds the dimensions of the corresponding part of any 

 of the other corallines. IVIy inability to discover it, though resorting to 

 numerous specimens of every size and age, has been already explained. 

 But I have witnessed it very satisfactorily in the present subject, under 

 peculiar circumstances, not by one, but by repeated observations. 



When the hydra is brought into a horizontal position, dark particles 

 are seen ascending one side of the neck and descending by the other, as 

 if conveyed by the current of a fluid. But the sides of the channels con- 

 taining them are invisible, perhaps, from tenuity ; nor is it undoubted that 

 the currents absolutely flow on the opposite sides of the animal, for the 

 channels may be separated by a smaller interval. Relative position in ob- 

 jects so minute is extremely delusive. The current is chiefly visible at the 



VOL. I. I 



