CAtJDINA. 



97 



tions is much like that of leeches, and on this account these 

 Synaptae were long supposed to be a transition type between the 

 Radiates and worms. The body grows to a great length, often 

 half a yard and more, but constantly drops large portions from 

 its posterior part, by means of its own contractions, or breaks it- 

 self up by the expulsion of the intestines, which are very readily 

 cast out. The tentacles are hollow, consisting of a central rib 

 with branches from either side. In the Synaptae, as in all the 

 Holothurians, the madreporic body is placed near the mouth, 

 between two of the ambulacra, and opposite the fifth or odd one. 

 The tube, connecting with the central tube aroimd the mouth, 

 by means of which it communicates with the ambulacral tubes, 

 is very short. 



Caudina. {Caudina arenata Stimps.) 



Several other Holothurians are frequently met with on our 

 shores. Am ong them is the Caudina arenata (Fig. 126), a 

 small Holothurian, yellowish in color, and thick in texture. 



Fig. 126. 



by no means so pretty as the white transparent Synapta ; the 

 tentacles are short, resembling a crown of cloves around the 

 mouth. It lives in the sand, and may be found in great numbers 

 on the sandy beaches after a storm. 



Fig. 126. Caudina arenata *, natural dae. 



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