222 ZOOPHYTES. 



in some specimens, but less definitely so in others. The cell is sessile or 

 without the intervention of any pedicle or twig connecting it to the stalk. 

 —Fig. 23. 



The hydra is well exposed through the sides of its transparent cell, 

 when the body is discovered as originating immediately from the internal 

 pith of the stem, or branch whereon the cell is sustained. It is of much 

 smaller diameter than the cell, tapering regularly downwards, and ascends 

 • to display from eight to fourteen deeply muricate tentacula. This great 

 irregularity of the number occurs on the same specimen. — Fig. 24. There 

 is likewise a difference in the form of the cells, from which those of the 

 same specimen are not exempt. But it is most conspicuous on the com- 

 parison of several. — Fig. 25. The lip of the bell is even. The general 

 asjject of the adult hydra is greenish-yellow. Vivid grass-green distin- 

 guishes the hydra itself and all later accessions. The cells are of the faint- 

 est yellow, older formations are brown. 



Probably the hydra is regenerated. In its progressive advances it is 

 seen in a long clavate shape, through the side of the cell, with some en- 

 largement of the pith at the point whence it originates. 



Short shoots frequently issue from each extremity of a section, which, 

 if vigorous, bear hydraj, but if feeble, they extend irregularly and prove 

 abortive. — Fig. 24, a. 



It seems a general law with the greater part of the Sertularian tribes, 

 that hydrae shall develope from all vigorous vegetation conveying the pith. 

 But nothing animated comes of what is feeble and irregular. 



Nevertheless, the precise order of the new subsidiary parts is dis- 

 turbed on the contact of such vigorous vegetation with solid substances. 

 A section of this Sertularia had generated a shoot an inch long, which in 

 seven weeks had run in adhesion along the bottom and up the side of a 

 vessel. Three cells with hydraj sprung from the horizontal portion on the 

 bottom ; and one, which was abortive, from that on the side. These four 

 would have stood in jjairs, nearly opposite, had the stem been free. Now 

 the whole rose from the upper side only. Long shoots, bearing cells with 

 hydrac, were at the same time vegetating from the lower extremity of 

 other two sections. 



