CHAPTER 9 



THE EYES OF ECHINODERMATA 



This phylum includes the star-fishes, Asteroidea ; the sea-urchins, 



Echinoidea ; feather-stars, Crinoidea ; and sea-cucumbers, Holothuroidea. 



Eye-spots are found at the bases of the terminal tentacles, which spring 



Fig. 60. 



Semi-diagrammatic drawing of a very young Asteroid, showing the positions of 

 the optic cushions — oc. — at the base of each terminal tentacle, or. : mouth. 



Each eye-spot is connected by the superficial or epidermal radial nerve of the 

 corresponding arm with one of the angles of the " nerve pentagon " which 

 surrounds the mouth. The ocelli are of a bright red colour. 



(From Arnold Lang, Textbook of Comparative Anatomy.) 



93 



