ACEPHALA. 245 



without which, suffocation and death would infalli- 

 bly ensue ? Secondly, how is the food conveyed to 

 the mouth ? for fixed as it is, and unfurnished with 

 any seizing organs, and unable to protrude any part 

 of its body beyond its stony abode, it is not easy to 

 imagine by what means a due supply of nutriment 

 is provided. 



" Wonderful indeed is the elaborate mechanism 

 employed to effect the double purpose of renewing 

 the respired fluid, and feeding the helpless inhabi- 

 tant of these shells. Every filament of the gill-fringe, 

 examined under a powerful microscope, is found to be 

 covered with countless cilia, * in constant vibration, 

 causing, by their united efforts, powerful and rapid 

 currents, which sweeping over the entire surface of 

 the gills, hurry towards the mouth whatever float- 

 ing animalcules or nutritious particles may be 

 brought within the limits of their action, and thus 

 bring streams of nutritive atoms to the very aperture 

 through which they are conveyed to the stomach, 

 the lips and labial fringes acting as sentinels, to 

 admit or refuse entrance, as the matter supplied be 

 of a wholesome or pernicious character. So energetic, 

 indeed, is the ciliary movement over the entire ex- 

 tent of the gills, that if any portion of them be 

 cut off with a pair of scissors, it immediately swims 

 away, and continues to row itself in a given direction 

 as long as the cilia upon its surface continue their 



* Cilia are organs of motion extensively found in the lower classes, 

 consisting of exceedingly minute hairs, endowed with the power of rapid 

 and regular motion. 



