244 



THE INHABITANTS OF THE SEA. 



Barnacle. 



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 

 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 



Balanus ovnlans. 



Development of Balanus balanoides.— (Acorn-shell.) 



A. Earliest form. B. Larva after second moult. C Side view of the same. D. Stage immediately 

 preceding the loss of activity, a. Stomach. 4. 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 



