132 



EOHINODERMS. 



present ; the eye, if so it can be called, in many species 

 consisting merely of a coloured spot, while in others 

 it is entirely absent.* 





Fig. 85.— Eye-spot of Lizzia (after 

 Hertwig). oc, Ocellus ; I, leus. 



Fig. 86. — Eye-bulb of Astropecten (after 

 Haeckel). 



In the Eehinoderms, the eyes, which were discovered 

 by Ehrenberg, have been described by Haeckel,t 

 Wilson, J Lange, and others. § They are in some cases 

 situated, as in Astropecten, on a pear-shaped bulb 

 (Fig. 86). 



They consist of a lens (Fig. 87), supplied with a 

 nerve, and lying in a mass of pigment. In Solaster or 



* Allman, " Mon. of the Hydroids," Ray Society, 1871. 

 t "Ueberdie Augeuund Nerven der Seestevne,"Zeit.furWiss.,\o\. x. 

 X Transactions of the Linnean Society. 



§ Lange, " Beit. z. Anat. iind Hist, der Asterien und Ophinren," 

 Morpli: Jahrhuch, 1876. 



