13G HENIiY DAVIS ON A LARVAL CIRRIPEDE. 



The bird was well supplied with parasites (which. were mine by 

 prescriptive right), and cemented to one of its feathers was a 

 prettily marked chitinous shell that could or should only be one of 

 their eggs; True, a bivalve egg of a bird's parasite was unknown, 

 all such eggs bearing opercula, but some of the parasites found 

 with it were probably new ; then why not a new form of egg ? 

 —making a parallel case with the mollusca, the shells of some of 

 which, we well know, are operculated, while others are bivalved. 

 Having tried to hatch that egg myself, with the patience of an 

 old hen " setting" on a chalk nest egg — and with the same result, 

 I consigned it with the attached feather to a bottle of spirit, and, 

 recently opening the shell, found within it the swimming legs of 

 an undoubted Crustacean ; and so was led on, step by step, from 

 book to book, to identify my egg as an advanced larva (or pupa) 

 of the Cirripede — Lepas pectinata. 



Now, it having been represented to me that the members of the 

 Quekett Club might be glad to examine the disjointed shell, and 

 that a few explanatory notes would not be unacceptable, I briefly 

 give an account of the larval pedunculated Cirripedes, as gathered 

 mainly from Dr. Darwin's great work, while Mr. dirties has kindly 

 undertaken to exhibit the specimens. 



Dr. Darwin seems to have studied Lepas australis more than 

 any other form, and gives the life-history of that species in detail, 

 but, from what he says, there can be no doubt the observations 

 and statements apply equally to L. pectinata, the latter, however, 

 being, in all its stages, much smaller than L. australis. 



The larva, immediately after its escape from the egg, is nearly 

 globular ; the carapace flattened in front, and it is provided with 

 two long horns, two short ones, three pairs of limbs, and a simple 

 heart-shaped eye. The long horns are supposed to cover the unde- 

 veloped antennaa, which play so important a part in the third stage 

 of the creature's existence, while the smaller pointed horns soon 

 develop into a pair of antennae for present use. After a few moults 

 of the carapace, in the manner of the entomostraca, with com- 

 paratively slight changes in form, the active larva reaches the 

 second stage. In this the shell is compressed laterally, and, it 

 resembles a cypris, or minute mussel ; it has still three pairs of 

 legs, but these are moved backward, and with the prolongation of 

 the body, foreshadow the final larval form. The smaller pair of 

 antenna? disappear, but a second simple eye is added. 



