3446 



THE WORM -LIKE ANIMALS 



colored tufts; the lower surface being pure white, and the head end furnished with 

 a pair of ear-shaped lappets, in which the sense of touch appears to be concentrated. 

 The creature is shown clinging to a branch of seaweed, with the head elevated so as 

 to exhibit its lower surface, and feeling for a new surface of support. Planaria 

 gonocephala, figured on p. 3445, is one of the land forms. The general structure 

 of the intestine in all the animals of this group is shown in the illustration at the 

 top of the preceding page. 



GROUP OF UNCERTAIN POSITION 



To complete our account of the worms, mention must be made of the parasitic 

 families Orthonectidx and Dicyemidce, of which the serial position is uncertain. 



TUFTED PLANARIAN, Thysanozoum. 

 (Enlarged twice.) 



Rhopalura. A. Male; B. Female. 

 (Very much enlarged.) 



The members of the former inhabit 

 the body cavity of certain turbellarian 

 and nemertine worms and brittle stars. 

 They are minute, segmented creatures, 



scarcely exceeding the twentieth of an inch in length, and without digestive organs 

 or nervous system, but with the skin ciliated. The males are smaller than the 

 females, being in the figured Rhopalura only about half the size of the latter. 

 The Dicyemidce are ciliated, thread-like parasites, varying in length from about a 

 thirteenth to a fifth of an inch in length, and living in the kidneys of cuttlefish. 

 The body consists of a central portion, composed of a single long, fusiform cell, 



