12 ZOOPHYTES. 



single leaf, fig. 26. This leaf sometimes subdivides in an early stage, 

 fig. 26, a. Sometimes it attains large dimensions, fig. 1. Here an entire 

 specimen consisted of only three large leaves, originating from the stem. 

 If adults have advanced so far that subdivision ensues, a corresponding 

 form always results by enlargement of the parts with a curving edge. The 

 sole and overhanging cell being single, the next cells above the latter are 

 two, situated vertically ; eveiy higher row augments in number, and thus 

 the leaf broadens. But the exterior circular edge seems always generat- 

 ing new cells with hydra;. Herein the young may be discovered in various 

 immature stages. They are contracted, and perhaps invested by an in- 

 tegument. In those farther advanced the tentacula are so disposed as to 

 be compressed in a narrow ellipse, where the tips of the row may be enu- 

 merated with tolerable accuracy. Those hydra higher in position, or 

 furthest from the root, seem the least mature. 



The newer parts of a leaf, always with a curving edge, are distin- 

 guished by a clean, clear, transparent aspect, greatly differing from that 

 of the older portion, fig. 2. Sometimes recent foliaceous accessions are seen 

 united either to the entire, or to the mutilated edge of older formations, 

 or with those in decay. The uniting boundary, which belongs to the 

 recent part, consists of an indefinite number of cells, but they continue 

 augmenting upwards after such a manner, that the new and generating 

 product always tends by their aggregate to present the ordinary symme- 

 trical conformation of a leaf enlarging ; and the edge is circular. Three 

 recent accessions of this kind, all with living tenants, sprung from the 

 margin of an old leaf, the smallest consisting of about ten cells, the next 

 with about twenty, and the third with more. This mode of increment 

 advances conspicuously in all the foliaceous Flustroc. It is not so evident 

 in the Flustra truncata from the lighter colour, as when the darker hue of 

 the Flustra foliacca is contrasted with the newer portion. 



The precise medium of union between the leaf, thus renovating, and 

 the old portion, is not obvious ; and it is still more difficult to comprehend 

 how new cells and hydra; are generated beyond the apparent decaying line, 

 intercepting their communication with the original portion of the leaf. I 

 know not that any intermediate pith or medullary matter, like that so 



