METAMORPHOSES OF C1RRIPEDES. 103 



two main stages, but with many transitional intermediate 

 grades (answering to the successive moults in the first 

 stage of ordinary larvae), before they passed into the third 

 or pupal stage. And the first two stages in these egg-like 

 larvae of Cryptophialus, clearly seem to correspond with 

 the first two stages in ordinary larvae ; for in both the 

 chief changes are, the shortening of the terminal projection 

 — the increase in size and approximation on the ventral 

 surface of the anterior horns or cases for the antennae — and 

 the compression of the whole body. In all members of 

 the Thoracica, the metamorphosis seems to run a remarkably 

 uniform course. The larva in the first stage undergoes 

 several moults and slighter changes — how many is not 

 known — before arriving at its second main stage, which 

 has been observed only in one single instance ; and judging 

 from Cryptophialus, this second stage passes abruptly by 

 one moult into the pupal stage ; and this, certainly, passes 

 abruptly into the Cirripedial or mature stage. 



Zarvce, first stage. — The larvae in this stage are known, 

 amongst the Balanidae, in Balanus, Pyrgoma, Coronula, 

 Platylepas, and Chthamalus ; and these genera include all 

 the principal forms. Amongst the Verrucidae they are 

 known in its one genus, Verruca. Amongst the Lepa- 

 didae, in Scalpellum, Ibla, Alcippe, Lepas, Conchoderma, 

 &c. ; and in all these genera the larvae present no im- 

 portant difference — hardly any difference which could be 

 viewed as generic, were these larvae independent animals, — as 

 may be inferred, chiefly, from Mr.C. S. Bate's descriptions.* 

 The abstract given in my former volume was not accompa- 

 nied by any illustrations, and I have consequently here given 

 (PI. 29, fig. 8), a view of the larva, in the first stage before 

 moulting, of Scalpellum vulgar e •■ the natatory legs are not 

 drawn with accuracy, only the relative position of the several 

 organs having been carefully attended to. 1 have also had 

 copied from Mr. Bate's memoir, a figure of the larva (PL 29, 

 (fig. 9) of Balanus balanoides. in its first stage, before 

 moulting, with its ventral surface exhibited ; and another 

 figure (with a few trifling alterations made after examining 



* 'Annals and Magazine of Natural History,' vol. viii (2d series), 185], 

 Plates G, 7, and 8. 



