60 CXELENTERATA AND 



regularly distributed. Certain sea-cucumbers and brittle- 

 stars have feet destitute of suckers. 



The nervous system is exposed to the water in star- 

 fishes, but is covered by a series of plates in brittle-stars 

 and sea-urchins and is internal in sea-cucumbers. Eye- 

 spots are found at the ends of the rays in star-fishes ; in a 

 ring about the aboral region in sea-urchins and are want- 

 ing in Crinoids and brittle-stars and possibly in sea- cu- 

 cumbers. Special organs of smell exist on the under or 

 oral surface of the star-fishes as shown by physiological 

 studies. Otocysts are known in deep-sea genera. 



The ovarian openings lie in the angles of the rays or in 

 the vicinity of the mouth in star-fishes ; in a circle about 

 the aboral region in sea-urchins and on the lateral cirri in 

 Antedon. In brittle-stars there are four broad openings 

 on the side of the disk, called by some genital slits. By 

 many naturalists these are regarded as respiratory open- 

 ings. Holothurians generally have a single sexual open- 

 ing near the mouth. 



A madreporic body or convoluted prominence is well 

 marked in star-fishes and sea-urchins and hidden or want- 

 ing in snake-stars and sea-cucumbers. 



The sexes are ordinarily separate. Some star-fishes, 

 snake-stars and the sea-cucumbers are probably hermaph- 

 rodite. The Echinodermata have a direct or indirect de- 

 velopment, and some are viviparous. 



The Echinodermata of our coast are divided as follows : 



Free Crinoidea. 

 Body with pinnate rays, with jointed cirri on the aboral 

 region. 



As/eroidea. 

 Body stellate or pentagonal, with an aboral and oral 

 region, the latter only crossed by five or ten double radial 



