FLATWORMS 



Eye spots 



Anterior 

 proboscis sheath 



Stylet of 

 proboscis 



Retractor muscle 

 of proboscis 



Fig. 11.22. General features of a tvpical nemertine, Amphiporus pulcher: this is a dorsal view 

 of a female individual. The stvlet is so placed that it occupies the tip of the proboscis when 

 this is fullv everted. Note the relativelv simple reproductive system, consisting; of a series of 

 pouch-like ovaries, each with a separate external openins;, and the longitudinal ves.sels of the 

 primitive blood-vascular system. (Redrawn, after Burger, from C. G. Goodchild in F. A. 

 Brown, Jr., et al.. Selected Inverlehrnle Types, copvright 1950 by John Wiley and Sons, Inc., 

 printed by permission.) 



tines are known. Some of the marine forms are free-swimming (pelagic), but 

 for the most part they Hve burrowing in the bottom or among the growths of 

 animal and plant life of the ocean floor. One species lives as a commensal 

 within the mantle cavities of bivalve mollusks. Common American forms are 

 Cerebralulus lacteus, a burrowing species which may be several feet in length, 

 and Tetraslemma elegans, less than an inch long. 



341 



