110 BRYOZOA. 



The food appears to be retained for a considerable time in the 

 stomach, and may be frequently seen to be regurgitated into the 

 gizzard, whence, after having been again submitted to its opera- 

 tions, it is returned to the stomach. Here it is rolled about by the 

 contraction of its parieties, and at its upper part is frequently sub- 

 mitted to a rotating motion. This rotation of particles is chiefly 

 near the pyloric orifice ; and a mass may be occasionally seen pro- 

 jecting through the pylorus into the intestine, and rotating rapidly 

 in the direction of the axis of the orifice. In an animal having a 

 similar form of pylorus to this, but in which the parts were more 

 transparent, I could distinctly see the cilia by which this rotation 

 is effected surrounding the orifice." 



The granular matter, after rotating for some time at the pylorus, 

 (a provision for preventing its too rapid escape from the stomach,) 

 passes into the intestine, where it accumulates in little pellets, 

 which are rapidly pushed by the contraction of the intestine to- 

 wards the anal orifice, through which they are expelled from the body. 



The tube or cell inhabited by this bryozoon is of exquisite struc- 

 ture, and the mechanism concerned in the protrusion and retraction 

 of the animal of great simplicity and beauty. 



The inferior two-thirds of the cell in the species under considera- 

 tion is hard and corneous, but perfectly transparent : the upper 

 third, on the contrary, is flexible, and so constructed as to form a 

 very complete operculum by which the entrance is guarded. The 

 flexible part consists of two portions, the lower half being a simple 

 continuation of the rest of the cell, while the upper is composed of 

 a circle of delicate bristle-shaped processes or setse, which are ar- 

 ranged parallel to each other around the mouth of the cell, and are 

 prevented from separating beyond a certain distance by a membrane 

 of excessive tenuity which connects them ; this membrane is evi- 

 dently analogous to the infundibular termination of the cells of 

 polyps already described. 



When the bryozoon retires into its abode, the setse and soft ter- 

 mination of the cell are gradually folded inwards in the manner 

 exhibited in the annexed figures (Jig. 46), which represent the 

 various stages of the process. The esophagus surmounted by its 

 tentacula descends first, whilst the integument of the upper part of 

 the body begins to be inverted at the point where it has its insertion 

 around the base of the tentacles (c). As the descent of the tenta- 

 cula proceeds, the inversion of this membrane continues ; and when 

 the extremities of the arms have reached the level of the extremi- 



