16 CIRRIPEDIA. 



its first stage bears a very close general resemblance, in 

 having three pairs of natatory appendages, the first being 

 uniramons and the two others biramons, and in having a 

 single eye on its broad anterior front, to the larvae of most 

 Entomostracans; but I cannot avoid the belief, that this 

 resemblance is only apparent, and not essential j and of 

 false resemblances, how many instances occur in the animal 

 kingdom ! In the larva, when first freed from the egg, both 

 pairs of antenna? are in process of formation within en- 

 velopes : the mouth is probosciformed and capable of move- 

 ment, but is destitute of gnathites ; it occupies a position 

 between the three pairs of natatory limbs ; and these limbs 

 I must believe, for reasons hereafter to be assigned, 

 answ r er (improbable as I am well aware it must at first 

 appear) to the second, third, and fourth thoracic legs of the 

 archetype Crustacean : the two hinder pairs of limbs appa- 

 rently soon become captorial, or fitted to secure prey. Now, 

 I cannot find in the published accounts of the larvae of 

 Entomostracans, any that answer to this description. 



The larva in the last 'stage might be included in the 

 vast class of Entomostracans : the attachment of the eyes 

 to the singular apodemes produced inwards from the basal 

 segment of the great prehensile antennae, and the develop- 

 ment of only the posterior six pairs of thoracic limbs, are its 

 chief peculiarities : but its rudimentary mouth, owing to its 

 transitional or pupal condition, renders the assignment of 

 its proper rank difficult. 



Having now given this short comparative sketch of the 

 structure of a Cirripede, I may venture to express strongly 

 my opinion, that the group is formed on a distinct type; as 

 different from the other three or four main Crustacean 

 groups, namely, the Podophthalmia, Edriophthalmia, 

 Branchiopoda, and Entomostraca, as these differ from each 

 other ; the differences, moreover, being of the kind con- 

 sidered by the highest authorities on this subject, as the 

 most important. It should be observed that there is no 

 special blending at either end of the Cirripedial series, 

 towards any one of the other main groups of Crustacea : 

 it is hardly possible to take some one Cirripede, and say 



