308 ON THE CLASSES OE THE 



are situated on each side of the base of the antennae, haye 

 their analogous and corresponding formation in Daphnia, 

 as may be seen in the seventh volume of Degeer, PI. 27. 

 Fig. 3. n. m. The anus of a Cirripede is placed at the 

 back of the proboscidiform tube, and is protected at each 

 side with a horny spinous process. The tube itself is 

 hollow, and terminates at the point with an orifice serving 

 as an opening for the oviduct, which is represented by 

 some authors as crowned with two or three hairs. Now, 

 all this description applies with equal truth to a Daphnia. 

 The eggs have in both animals the same position, being 

 heaped together along the back between the shell and the 

 great intestine. The intestinal canal has two cascums in 

 one, as well as in the other. Their nervous system is 

 formed on the same general plan, and apparently their or- 

 gans of manducatioh. The heart is also dorsal in both, 

 and in short the important question seems to respect the 

 point in which there is any difference between them. This 

 difference however is by no means trifling ; for the Cirripedes 

 are deprived of the power of locomotion, and consequently 

 are hermaphrodites; they are likewise destitute of a head, 

 and their body, properly so called, is not accurately speak- 

 ing articulated. That vegetative quality by which they 

 are rendered incapable of locomotion is truly the natural 

 character of the group ; for, as we proceed, we shall find 

 that the cartilaginous peduncle which in the Pentelasmis 

 merely served as a cable, by means of which the animal 

 was fixed by the back of the thorax to its anchorage, be- 

 comes in the Balani the most important part of the whole 

 structure. The Crustaceous animal gradually disappears 

 sinking into the peduncle, which becomes calcareous, and 

 no vestige remains of the Cirripede shells which we have 



