132 



ECHINODERMS. 



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, lens. 



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

 Haeckel). 



In the Echinoderms, the eyes, which were discovered 

 by Ehrenberg, have been described by Haeckel,t 

 Wilson,t 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 witli a 

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



• Allman, "Mon. of the Hydroids," Bay Society, 1871. 

 t " Ueber die Augen und Nerven der Seesterne," Zei7./Mr TTm., vol. x. 

 X Transactions of the Linnean Society. 



§ Lange, •' Beit. z. Anat. und Hist, der Asterien und Ophiuren," 

 Morph. Jahrhuch, 1876. 



