HOLOTHURIOIDEA 



A HOLOTHURIAN OR SEA CUCUMBER 



I SEA CUCUMBER 155 

 

 ater of the New England coast are suitable for this dissection 

 - Thyone briareus and Cucumariafrondosa, the former being com- 

 on in Vineyard and Long Island Sounds and the latter on the 

 iaine coast. The latter is the larger of the two species, being 

 from 10 to 25 cm. or more long and about half as thick, and 

 differs from Thyone, among other things, in having ambulacral 

 feet in the radial areas alone ; it possesses thus five broad bands 

 of these appendages, the interradial areas being smooth. Thyone 

 is from 8 to about 20 cm. long and 5 cm. thick, and is covered 

 all over with ambulacral feet, the five broad radial bands meet- 

 ing in the interradial areas. It will be used as the basis of this 

 dissection. 



Observe the form and color of the body. Note that the upper 

 and lower sides are distinctly differentiated, the former having 

 fewer feet than the latter. In the center of the forward end is 

 the mouth, surrounded by the ten branched tentacles by means of 

 which the animal collects the minute organisms which constitute 

 its food. Above the mouth and between the bases of two ten- 

 tacles is the genital pore. In the center of the hinder end is the 

 anus, surrounded by five anal teeth. The main longitudinal axis 

 of the body (that which joins the mouth and the anus) will thus 

 be seen to be very long, in sharp contrast to that of the starfish 

 and sea urchin, in which it is much shorter. In consequence of 

 this feature the body is elongate and more or less worm-like, and 

 the animal does not rest on the oral surface but on its side. 



Exercise l. Draw a side view of the animal and label carefully 

 all of the features observed. 



