CHAPTER 8 



THE EYES OF MOLLUSCOIDA 



The Molluscoida are marine animals comprising three classes, the 

 Polyzoa, Brachiopoda, and Phoronida. The Polyzoa form colonies known 

 as " sea-mats " or " coral-lines." The Brachiopoda are characterized by 

 the possession of bivalve shells which differ from those of the molluscs in 

 being dorsal and ventral with regard to the animal instead of right and left 



hb.-,^g 



oc. 



,.. P t, 



— mtr 



stom/ 



Fig. 58. — Trochopore Larva of Phascolosoma vulgare, showing the Typical 

 Position of the Paired Eye-spots in the Podaxonia (Sipunculoidea). 

 ap. : apical tuft of cilia. oc. : eye-spots. 



head blastema. stom. : stomodajum. 



metatroch. tb. : trunk blastema, 



prototroch. 



(From McBride, after Gerould.) 



h.b. . 

 mtr. 

 ptr. . 



as is the case in molluscs. A typical example of the class is the common 

 " lamp shell." The Phoronida are worm-like animals enclosed in 

 leathery tubes. They live in associations composed of numerous indivi- 

 duals each of which possesses a number of tentacles springing from a horse- 

 shoe-shaped pedicle, the lateral horns of which are often spirally coiled. 

 The body is strongly flexed in a dorsal direction, so that the mouth and 



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