22 CIRRIPEDIA. 



beautiful discs of teeth, and brushes of hairs, — a structure 

 confined to this order. The male resembles the male of 

 Alcippe ; and the latter genus seems to be the connecting 

 link between the Thoracica and Abdominalia. But the 

 most important character of this latter order, in which it 

 differs from Alcippe, and all other known Cirripedes, is in 

 its metamorphoses ; all the first changes are merely indicated 

 by changes in form in an egg-like larva, without the de- 

 velopment of distinct organs ; and the last, or pupal condi- 

 tion, which is attained within the sack of the parent, is very 

 peculiar, by the entire absence of natatory limbs. 



The third order of Apocla is the most peculiar of all ; it con- 

 tains, like the last, only one known species : the most acute 

 naturalist, I am convinced, if he had not made the class his 

 special study, would never even have suspected that this 

 animal was a Cirripede. We see much magnified in PI. 25, 

 fig. 7 a naked, plainly-articulated animal, resembling the 

 larva or maggot of a fly, attached by two threads ; and these 

 threads, on analysis, can be clearly shown to be the last rudi- 

 ment of the carapace, specially modified. The last cephalic, 

 the seven thoracic, and the three abdominal segments, are 

 all equally destitute of appendages. The mouth is suctorial, 

 and constructed on a plan unlike, I believe, anything known 

 in the articulate kingdom ; for the mandibles and maxillae 

 have rotated on their axes, and stand back to back ; they 

 can act only by tearing open a slit, and this action is per- 

 formed in a hood, formed by the confluence of the broad 

 palpi and labrum. Although the oesophagus is distinct, 

 there is no stomach or anus. Lastly, owing to there being- 

 no carapace, the ova are developed, differently from in all 

 other Cirripedes, within the thorax. 



I will close this preliminary discussion on the confines 

 and type of the sub-class, by recalling attention, now that a 

 sketch has been given of the three Orders, to the remark 

 before made, that a wide range of structure is included 

 within it, and by reurging that the Cirripedia should be 

 ranked, not as one of the subordinate groups, but as one 

 of the main divisions of the Crustacea. 



