METAMORPHOSES OF C1RRIPEDES. 107 



Mr. Bate's observations, to have the power of movement. 

 It is directed posteriorly, the oesophagus extending ante- 

 riorly; both these directions being the same as in the 

 mature cirripede. Certainly during these early stages there 

 are no jaws or gnathites ; but the margin, answering to the 

 labrum, is furnished with some short, thick, sharp spines, 

 and with hairs. In Scalpellum vulgare the orifice of the 

 oesophagus seems to lie rather beneath the upper prominent 

 spinose edge, which, as just remarked, probably answers 

 to the labrum ; but this is one of the species in which the 

 probosciformed mouth, at least before the first moult, is not 

 much developed. 



We come, now, to the three pairs of natatory legs : the 

 first (PI. 29, figs. 8 — 10, e) has throughout the order only 

 one ramus, whereas the two succeeding pairs (f,g) are 

 biramous. I must here remark that the straight and strong, 

 and the curved plumose spines, with which these limbs, 

 after the first moult, become furnished, now appear to me 

 as more probably prehensile, rather than masticatory as I 

 imagined in my former volume. That these spines are 

 important organs to the larvae I do not doubt. With 

 regard to the homologies of these three pairs of limbs, my 

 first impression was that they were the mandibles and 

 the two pairs of maxillae in their earliest condition ; but I 

 consider this view as quite untenable, for several reasons ; 

 viz., the wide interval between their bases and the mouth 

 itself, — the somewhat variable position of the mouth with 

 respect to the legs, — and the position which the latter 

 occupy in the second larval stage.* A far more tenable 

 view is that these three pairs of legs are the three pairs of 

 maxillipeds, in their earliest condition, in accordance with 

 the view of M. Jolyf on the nature of the three very similar 

 pairs of natatory legs in the larva of Caridina, a macrourous 

 Crustacean. But, in Cirripedes, the three pairs of natatory 



* Mr. Dana, moreover, has remarked, (' Crustacea : United States Exploring 

 Expedition,' p. 1386), "that he knows of no instance of a mandible becoming so 

 completely a leg, as to lose wholly the mandibular function even of its basal 

 portion." 



t 'Annales des Sciences Naturelles,* 2d series, torn, xix, 1843, p. 34. 

 M. Joly's observations were made on the Caridina. I owe to the great kind- 

 ness of Mr. C. Spence Bate, an examination of some larvee of the allied genus 



