IN THE SECOND TYPE OF THE CIRRIPEDES. 357 



last probably did not possess sufficient vitality to pass into the next stage, such as 

 we see that of Lepas anserifera (fig-. 5.). 



The larva of the Lepades, then, is a tailed Monoculus, with three pairs of members, 

 the most anterior of which are simple, the others bifid, having its back covered by an 

 ample shield, terminating anteriorly in two extended horns, and posteriorly in a 

 single elongated spinous process*. 



It must ever remain uncertain how long the larvae of the Lepades remain in their 

 first or free state, but it is probably for a longer or shorter period of time, according 

 as they sooner or later meet with a substance adapted to their respective habits : 

 thus, those of the Lepas fascicularis attach themselves in preference to Gulf-weed 

 or floating Fuci ; Lepas minima to slender species of Antipathes ; Lepas anserifera^ 

 and dentata, Cineras vittatus, and Otion, to the bottoms of ships ; Lepas anatifera% to 

 floating timber, and to one another; w\\\\q Lepas sulcata seems to prefer the backs of 

 Turtles and the shell of the lanthina : the species, however, have not been sufficiently 

 discriminated, nor observations of this kind made with the requisite care, to enable 

 us to prosecute further this part of their natural history. It is evident that they 

 possess locomotive powers which enable them at every instant to change their situa- 

 tion, and a conspicuous eye to guide them in their choice. 



These remarkable and important discoveries, connected as they are with those re- 

 lating to the Crustacea §, complete the natural history of this tribe, and lead us to 

 the following important results, viz. 



I. That the Cirripedes do not constitute a distinct class of animals, as they have 

 been considered by all late naturalists. Dr. Leach, Latreille, Lamarck, Cuvier, &c., 

 being connected with the Crustacea decapoda through the Balani, and with the En- 

 tomostraca by means of the Lepades. 



II. That they have no relation or affinity whatever with the Testacea, as supposed 

 by LiNNiEus and all the older systematists. 



III. That the Crustacea now therefore furnish examples of a class in which we have 

 animals free and fixed, with eyes and eyeless, and with the sexes separated in some 

 and united in others, all of which are characters to which naturalists have attached 

 the greatest importance as regards classification. 



IV. That the proof of metamorphosis being fully and satisfactorily established, tends 

 still to maintain the affinity so long recognised between the Crustacea and Insecta. 



Note. — The same economy in regard to the disposal of the ova has been observed 

 in Otion, but hitherto no individual has been found with the ova on the point of 

 hatching. 



* Compare with the larva of Artemis (Brine Shrimp). Zoological Researches, No. v, Plate II. f. 7, 8. (here- 

 with sent). 



t Philosophical Transactions, vol. i. Plate xxxiv. fig. 5. 

 X Philosophical Transactions, vol. i. Plate xxxiv. fig. 6, 

 § Zoological Researches, Memoir I. and Addenda, p. 63. 



