ANTENNA OF ROTIFER. 39 



or feeler, and brings its possessor in further relation 

 to the external world. It is also called the calcar^ 

 or spur, and is furnished with cilia or bristles at 

 its extremity. 



Sometimes the particles swallowed by the Common 

 Rotifer are large enough for their course to be traced, 

 but there is more frequently a great commotion 

 and grinding of the gizzard, without any appreciable 

 cause, although doubtless something is taken in, and 

 when the creature is tired, or has had enough, we 

 see both head and tail retracted, and the body 

 assumes a globular form. In another chapter, when 

 viewing a Fhilodine, we shall see how in the family 

 to which the Common Eotifer belongs, the gizzard 

 departs from the perfect type. 



