ON POLYPS. 



dilated. After a few hours the branch is visibly longer, its 

 extremity more swollen, and the living pith is seen partially to 



Fig. 15. 



f 



have separated itself from the sides of the tube, the boundaries 

 of which become more defined and undulating (2). The growth 

 still proceeding, the extremity is distinctly dilated into a cell, in 

 which the soft substance seems to be swollen out, so as to give a 

 rude outline of the bell-shaped polyp (3), but no tentacula are yet 

 distinguishable ; a rudimentary septum is now visible stretching 

 across the bottom of the cell, through the centre of which the 

 granular matter, now collected into a mass occupying but a portion 

 of the stem, is seen to pass. The polyp and cell gradually grow 

 more defined, (4, 5, 6,) and the tentacula become distinguish- 

 able ; the cell, moreover, is seen to be continued inwards by a mem- 

 branous, infundibular prolongation of its margin (7), which imme- 

 diately reminds us of the funnel-shaped membrane of Tubipora 

 ( 50), and its office is no doubt similar. As the developement 

 proceeds, the tentacles become more perfect (8), and the polyp at 

 length rises from its cell to exercise the functions to which it is 

 destined. 



(69.) The third mode of multiplication, or that by reproductive 

 gemmules, seems to be specially adapted to the diffusion of the 



