100 INTRODUCTION TO POLYZOA, 



in which the ultimate results attained are so 

 utterly unlike the origin, that were not all the 

 various stages of evolution traceable, it would 

 have appeared incredible that this organ 

 should have originated, as it has done, in the 

 ordinary Polypide and cell. To describe, then, 

 briefly, this peculiar organ, which occurs only 

 in that group of the Polyzoa in which is found 

 the lip-like door, viz., the Cheilostomata. 



In examining (with the microscope) the 

 colonies of certain species, some members are 

 found to differ somewhat from the ordinary 

 members. The cell becomes gradually reduced 

 in size and the aperture with its door becomes 

 larger in proportion to the cell area, and also 

 modified in form, approaching somewhat to 

 the shape of a bird's beak. The size of the 

 cell becomes still further reduced until it is 

 quite small comparatively with an ordinary 

 cell. The cell outline now becomes partly or 

 wholly obliterated, and the cell commences in 

 consequence to lose its identity as a distinct 

 cell, and gradually becomes merged in a 

 neighbouring one. The Polypide has become 

 aborted, but well-developed muscles occupy 

 its former position. These serve for opening 



