SOCIAL "CROWNED HEADS." 133 



This vibratile motion brings the fine particles of 

 decomposing animal and vegetable matter in the 

 water to the mouth, which is situated just in the 

 bend of the heart- shaped crown, whence, by the 

 same action, it is carried down the gullet to the 

 complex gizzard or masticatory apparatus, and 

 triturated or ground down to the finest imaginable 

 pulpy material for digestion and assimilation in 

 the tissues of the body. 



The trochal crown or head is not an open 

 orifice, as, from the lappet-like expansion of the 

 ciliated disc which runs round, one would at 

 first sight be inclined to suppose, but is covered 

 with a fine, gauzy, delicately-marked, and figured 

 membrane, which, at times, is gently raised above 

 the surrounding ciliated disc, as if from an up- 

 ward pressure from beneath, where are situated 

 the eyes and nerve ganglia, or brain. The most 

 prominent distinguishing characteristics in Me- 

 yalotrocha as compared with Lacinularia, are four 

 white opaque dots, placed like a row of 

 pearls around its neck. These are equi-distant 

 from each other, except at the bend in the 

 crown, just below the mouth, where the distance 



