118 ZOOPHYTES. 



The preceding was among my earlier observations. Their extension 

 and confirmation were desirable ; especially from such subjects being rare 

 and unmanageable. 



Long afterwards, I availed myself of the under valve of a large speci- 

 men of the Pecten Jacobmis, a kind of clam-shell, which bore about 150 

 of the Hydra tuba, when withdrawn from the sea on the 21st of March. 

 The external convexity was invested by the white Alcyonium digitatwn or 

 Lobular ia : and a portion of the concavity, occupied by tubes of the Tere- 

 bella, with and without their tenants. Having extirpated the former, and 

 the surface being carefully brushed perfectly clean of impurities, and the 

 latter, to which many hydrse were adhering, having been removed, I com- 

 puted that about 110 specimens remained, distributed over the inner sur- 

 face of the valve. The outside was quite free of them. 



All were of very moderate dimensions, having probably dwelt in a 

 barren place, as animals of this kind enlarge so readily where subsistence 

 abounds. Some were sjTnmetrical and perfect, with an ordinary comple- 

 ment of long flowing tentacula. 



But, at least one-half of this numerous colony was undergoing a re- 

 markable change ; and to an indifferent observer, the shell had no distant 

 resemblance to a surface overspread by above fifty grains of rice affixed by 

 one end. 



Those thus distinguished were interspersed promiscuously amongst 



the rest. 



They exhibited various features. For the most part the hydrae de- 

 finitely affected consisted of a smooth bulbous base, root, or foundation 

 next the shell, surmounted by an indented or whirled cylinder, which was 

 crowned by a circle of sufficiently active tentacula. The peculiar position 

 of these hydrae denoted little distinction ; all were pendent according to the 

 nature of the tribe, some inclined and others curved slightly as they hung. 



PI. XIX. fio-. 1, portion of the shell and subjects somewhat enlarged. 



Figs. 2, 3, subjects nearly according to Nature : the latter as they ap- 

 peared a week later than in fig. 1, on March 29. 



Many of these subjects were now environed by plain circles, as if 

 faintly indicating segments ; fig. 4, enlarged. 



