HENRY DAVIS ON A LARVAL CIRRIPEDE. 137 



Of the larva in its third stage (in which it is sometimes called 

 the "locomotive pupa"), Darwin gives a figure; and this, with 

 certain additions to the carapace, will answer for the specimen now 

 before you. Of the internal parts of the latter the only portions I 

 could mount were the natatory legs and caudal appendages ; the 

 rest, being soft and oily, were decomposed — no doubt in my vain 

 effort at incubation. 



In PI. xiii., Fig. 1, one valve is removed, and the swimming legs 

 and appendages are seen at C and D. Just above the feet are 

 dimly indicated the immature cirri of the perfect barnacle ; at M 

 the mouth, and at N the supports of the internal eyes — now com- 

 pound. The remainder of the anterior inner part is occupied by 

 cement-secreting glands, the incipient muscles of the young 

 barnacle's foot, and, outside all, the prehensile antennae. 



Hitherto we have seen the creature in a free state ; in the last 

 stages swimming on its arched back, or crawling with the aid of 

 its antennae ; it has now to settle down quietly and for the 

 remainder of its life. This it does by holding on to the selected 

 object by its antennae, and pouring over them, from special glands, 

 a liquid cement which permanently glues them down. After this 

 the animal sheds its larval legs, eyes, and carapace ; while the 

 straightening-out of the peduncular muscles, consequent on the 

 moult, draws the entire Cirripede from a position parallel to the 

 attached surface to one at right angles to it (see Fig. 2). If 

 this change of position were not effected the barnacle could only 

 use its cirri against the object to which it was fastened, and its 

 capture of food would be extremely limited. 



Of the Cirripede in its perfected stage little need be said, we are 

 all familiar with its external form, its fleshy peduncle terminating 

 with calcareous valves enclosing the body and delicate casting-net; 

 but a mature specimen of a Lepas, with some of the valves 

 removed, is now before you under a low power, and this might 

 teach more than a volume of words. 



I should add a line as to measurements. The egg and youngest 

 larva of L. australis are about y-goth °f an mcn ^ 0Yi Si ^ ne iarva m 

 last stage is nearly T Vh of an inch, and the well- grown Cirripede 

 nearly two inches, including the peduncle. The larva of our Lepas 

 pectinata is about y-g-th of an inch long, and, had if, not been pre- 

 maturely cut off, might have grown fully three quarters of an inch. 



The small amount of original matter I can offer on this animal 



