604 ORDER APODA. 



Fourthly : in the male Ibla the capitulum is so much 

 atrophied that it does not inclose the thorax or mouth, but 

 still an elongated support or peduncle is left. But it 

 would be no very violent assumption to imagine the 

 peduncle, which does not essentially differ from the capi- 

 tulum, to become likewise rudimental, — to grow smaller and 

 smaller, and shorter and shorter, till the merest remnant was 

 left at the spot where it entered the cemented antennae. 

 And in the last paragraph it has been shown that it would 

 be no violent assumption to imagine this lower end of the 

 peduncle, where it enters the antennae, developed into 

 two short thread-like prolongations. 



Lastly: it is certain, from the existence of the pre- 

 hensile antennae, that Proteolepas was developed within a 

 pupa, probably differing in no very essential respect from 

 the pupae of other cirripedes. Therefore, in accordance 

 with all analogy, we may believe that the position* of 

 the young Proteolepas (probably much coiled up, with a 

 deep fold close under the mouth) within the pupa, the general 

 form and structure of the latter, and the course of the 



* Any one who has not specially attended to the metamorphoses of ordinary 

 cirripedes, who looks at the imaginary figure of the young Proteolepas, will 

 feel much surprise at the relative positions of the parts; for the mouth and 

 the first and even second segments of the body stand posteriorly («. e. above in 

 the figure) to the succeeding segments of the body, in relation to the carapace of 

 the pupa ; but this is only in accordance with the remarkable change in posi- 

 tion (as explained in the introduction, p. 123, pi. 30, fig. 2), amounting almost 

 to inversion, which the whole thorax of every young cirripede undergoes within 

 the pupa, whilst the anterior cephalic portions and general covering are de- 

 veloped conformably with the pupal carapace, whence it arises that the dorsal 

 surface of that part of the thorax immediately succeeding the mouth becomes 

 attached to the ventral internal surface of the carapace. I believe that the 

 peculiar flattened dorsal outline of the first two segments of the body of Proteo- 

 lepas is due to these parts having been formed in contact (as represented in 

 pi. 25, fig. 6) with the straight ventral surface of the carapace of the pupa. To 

 place the young Proteolepas, and at the same time the carapace of the pupa, 

 with all the parts in proper homological sequence, it would be necessary to 

 seize the posterior end of the abdomen (#), and pull till the dorsal surfaces of 

 the first and second segments of the body, separated from the ventral internal 

 surface of the carapace, and stood posteriorly (i. e. above in figure) to the mouth, 

 which latter would thus also have to rotate a quarter of a circle, so that the 

 orifice would come to be directed outwards. Then every part would stand, 

 in accordance with the archetype crustacean structure, in due order; but the 

 three confluent anterior cephalic segments, forming the front part and carapace 

 of the pupa, would, as in the case of all cirripedes, be of disproportionately large 

 size in relation to the rest of the body. 



