334 POLYZOA INFUNDIBULATA. 



-Cellularia scruposa, and immediately in front of the tooth-like pro- 

 cess there attached, are two pretty long spines and a rounded pro- 

 cess, which tapers slightly from its fixed to its free extremity. This 

 rounded process is open at the top, and is hollow in dead specimens; 

 but when alive it is full of a contractile substance. In this contrac- 

 tile substance the end of a hair-like curved filament, about the 

 length of the cell, is immersed. This hair-like filament is moved 

 about by the contractile substance attached to it, generally in jerks 

 after intervals of repose, and in its movements sweeps the anterior 

 and posterior surfaces of the cell to which it is fixed. These move- 

 ments continue for a considerable time after the animal inhabiting 

 the cell has been dead. A hollow rounded process, with a hair-like 

 curved and moveable filament projecting from it, is also fixed upon 

 the corresponding part of each cell of the Cellularia reptans. These 

 moveable hair-like filaments are analogous to the moveable bird-head 

 process attached to each of the cells of Flustra avicularis." 



The organic relations of these appendages are very obscure, for 

 nothing similar is to be found in any other class of animals ; and 

 the use of them to the polypes is merely conjectural. This may be 

 two-fold. By those formed in the model of pincers the polype may 

 seize circumfluent animalcules, for although they are too short to 

 hand the prey to the mouth, yet retained in a certain position, and 

 enfeebled or killed by the grasp, the currents set in motion by the 

 ciliated tentacula, may then carry it within reach. The hair-like 

 bristles are more probably organs to drive away any injurious par- 

 ticles or animalcules that might seek an entrance into the cells. Pro- 

 fessor Reid says, " The use of these hair-like prolongations may 

 probably be to keep the surface of the polypidom clear of substances 

 which would otherwise adhere to it. Their motions are executed 

 with more force than we should at first suspect. I have seen one of 

 them in its course encounter the stalk of a Pedicellina echinata, and 

 press it aside." 



15 CELLULARIA,^" Pallas. 



CHARACTER. Polypidom calcareous or membrano-calcareous, 

 confervoid, divided dichotomously, the divisions narrow^ com- 

 posed of two or three alternating series of oblong contiguous 

 cells on a single plane, the apertures lateral, oblique and 

 facing one way. Polypes ascidian with usually 14 tentacula ; 

 no gizzard. 



* From ccltula, the diminutive of cella, a cell. 



