VII 



PHYLUM ECHINODERMATA 



171 



sharp tooth. The points of these five teeth can be seen 

 through the opening of the mouth. The enteric canal has 

 no radiating caeca. The five ducts of the reproductive 





FIG. 88. StrongylOCentrotUS, entire animal with the tube-feet extended. 

 (From Brehm's Thierleben.) 



organs open on five ossicles, the genital plates (Fig 90, gen.), 

 which with five smaller ocular plates (pc.) each bearing 

 a rudimentary eye, form a complete ring round the space 



