SEA CUCUMBER 155 
HOLOTHURIOIDEA 
A HOLOTHURIAN OR SEA CUCUMBER 
Two common species of holothurians which live in the shallow 
water of the New England coast are suitable for this dissection 
— Thyone briareus and Cucumaria frondosa, the former being com- 
mon in Vineyard and Long ‘Island Sounds and the latter on the 
Maine 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 1. Draw a side view of the animal and label carefully 
all of the features observed. 
