METAMORPHOSES OF CIRRIPEDES. 121 



become compound, of great size, and are attached to the 

 apodemes of the antennae: in the mature and fourth stage, 

 they have moved someway posteriorly, and again have be- 

 come simple, of minute size, and are either confluent, as in 

 the Lepadidse, or tolerably far apart, as in the Balanidse. It 

 must not be supposed that the eye of the mature Cirripede 

 is metamorphosed from the eye of the pupa, for such is not 

 the case ; the new eyes and old eyes being formed someway 

 apart, and frequently both can be seen within the pupa (as 

 in Alcippe, PL 23, fig. 16) at the same time. It is scarcely 

 possible that the eye of the larva in the first stage, can be 

 changed into the double eyes of the second stage ; though 

 these latter may possible be multiplied into the eyes of the 

 pupa, as both continue to occupy nearly the same position.* 

 Mouth, thorax, limbs, abdomen. — I have nothing to add 

 regarding the mouth, except to confirm my former account ; 

 viz., that it is functionless, consisting merely of crests, 

 which project inwardly between the gnathites of the young 

 Cirripede, and of a shrivelled closed tube representing the 

 oesophagus. In fact the mouth is a model of the outside 

 of the mouth of the young Cirripede. I may remark that 

 some little way beneath the membrane answering to the 

 labrum, a pair of ligamentous apodemes, the use of which I 

 do not know, slightly penetrate the body. The degree of 

 prominence of the mouth varies, but it is far less than in the 

 mature animal. On the limbs I have nothing particular to 

 add : the drawing of the first pair of legs (PL 30, fig. 5) is, 

 I think, very accurate : I observed all the spines here figured, 

 on the corresponding leg of the pupa of Balanus Hameri. 

 The five posterior pairs of legs differ only in the outer 

 ramus having five plumose spines, instead of four, and one 

 short simple spine at the exterior angle, making six alto- 



* Zenker, in his ' Physiological Remarks on the Daphnidse,' (' Journal of the 

 Microscopical Society, 5 1853, p. 274), speaks of a "tripartite azygous eye" 

 as common amongst Crustacea, and as occurring "in conjunction with the 

 aggregated eyes in Artemia, Argulus, &c. ; but as appearing regularly in all the 

 Branchiopoda and Siphonostomata as the earliest visual organ. Hence I con- 

 clude that this azygous eye is the homologue of that single eye which appears 

 in the earliest larval stage of Cirripedes ; and that the compound eyes of the 

 cirripedial pupa, answer to the aggregated eyes of Artemia and Argulus, &c, 

 with the difference, that in these latter genera the single eye is retained. See, 

 also, Von Siebold, 'Anatomie Comparee,' torn, i, p. 435. 



