244 THE INHABITANTS OF THE SEA. 
disposition, but frequent outbursts of an irascible and san- 
guinary temper. ‘Though the whole of the Crustacea are formed 
after one and the same 
general type, and the 
same fundamental idea 
may be traced through- 
out all their tribes, 
yet the rings of which 
Barnacle, their body is composed, 
and the limbs or ap- 
pendages attached to these segments, undergo such exten- 
sive modifications of structure in the various orders into which 
the class has been divided that even the eye of 
science has with difficulty made out the true 
nature of many of their lowest forms. Who, 
for instance, judging from outward appearances 
alone, would suppose that the Barnacles and 
Acorn-shells which he sees riveted to the rock 
or to a piece of floating timber were relations 
of the crab or lobster; but a view of their early 
forms at once points out their real character, for then they appear 
tt ES ec 
Balanus ovuiaris. 
Development of Balanus balanoides.—(Acornu-shell.) 
A. Earliest form. B. Larvaafter second moult. C. Side view ofthesame. D. Stage immediately 
preceding the loss of activity. a, Stomach, b. Nucleus of future attachment. 
as active little animals possessing three pairs of legs and a pair 
of compound eyes, and having the body covered with an expanded 
