290 
THE OCEAN WORLD. 
vegetarians. The organs of respiration of the Ecliinidf® appear to 
be certain flattened vesicles in the form of very delicate lamina?, which 
adhere to the internal sur- 
face of the walls of the 
body, and float freely in the 
liquid with which the vis- 
ceral cavity is filled. These 
organs, known as the in- 
ternal branehiee, are in com- 
munication with the central 
canal and ambulaeral tubes- 
The heart is spindle-shaped? 
tapering above, swelling 
below. There are two dis- 
tinct vascular systems, on e 
intestinal, the other cuta 
neons. 
Their nervous system con- 
sists of a ring, which sun 
rounds the gullet, and lS 
placed at a short distant 
Fig. 1 1 8. Skeleton and Masticating Apparatus. 
from the mouth. In this ring the nervous trunks have their origU 1, 
In relation to the senses, that of touch is highly developed. Certain 
branching tentacula, which surround the mouth, fashioned 1& 6 
nippers, and the ambulaeral tentacles, are its principal organs. The} 
appear to be altogether destitute of organs of sight. It has some- 
times been argued that four or five red points at the summit 0 
the dorsal face are eyes ; but this opinion has not been maintain 6 > 
nor has any “ crystalline ” been found in these spots to justify ^ ’ 
Captain de Conde states that he examined a sea-urchin with l°n$ 
spears in a pool of water, which he tried to catch, when he sa ^ 
it direct its flight towards his hand, all its defences being ei' eC ' 
Surprised at this manoeuvre, he tried to seize it from another quarter? 
its spines were instantly directed to the other side. “ I have tboug^ 
from that time that the urchin saw me, and prepared to resi 
my attack. In order, however, to satisfy myself whether or not ^ 
movement in the water caused by my approach might have produce 
the effect described, I repeated the experiment with greater caution 
