"356 MR. THOMPSON ON THE METAMORPHOSIS 



or the resemblance is still more striking to that of the Argulus Armiger of Latreille, 

 which, in fact, is but an Amymone furnished with a tricuspidate shield at the 

 back. 



The genus Cineras was the first in which the larvae were observed to hatch, July 27, 

 three days after the arrival of the ship ; then in Lepas anserifera, August 19 ; and a 

 few days later in Lepas dentata ; in all of which there is a perfect accordance, with 

 very slight differences, which probably resulted from the more or less perfect develop- 

 ment of the larva. The very remarkable and beautiful one of Lepas anserifera may 

 be regarded as the perfect type to which all the others are to be referred (fig. 5.). 



In the whole of this tribe of the Cirrlpedes, the ova, after expulsion from the ova- 

 rium, appear to be conveyed by the ovipositor into the cellular texture of the pedicle, 

 just beneath the body of the animal, which they fill to the distance of about an 

 inch. When first placed in this situation they seem to be amorphous, and inseparable 

 from the pulpy substance in which they are imbedded ; but as they approach to ma- 

 turity, they become of an oval shape, pointed at both ends, and are easily detached. 

 Sir EvERARD Home has given a very good representation of them, at this stage of 

 their progress, in his Lectures on Comparative Anatomy, from the elegant pencil of 

 Mr. Bauer. 



During the stay of the ova in the pedicle, they render this part more opake, and of 

 a blueish tint ; the ova themselves, and the cellular texture with which they are sur- 

 rounded, being of a pale or azure blue colour. It is difficult to conceive in what 

 manner the ova are extricated from the situation above indicated ; but it is certainly 

 not by the means suggested by Sir Everard Home in the above-mentioned Lecture, 

 viz. by piercing outwards through the membranes of the pedicle, for the ova are sub- 

 sequently found forming a pair of leaf-like expansions, placed between either side of 

 the body of the animal and the lining membrane of the shells in Lepas (fig. 1 .), or of the 

 leathery internal tunic in Cineras. These leaves have each a separate attachment at 

 the sides of the animal to the septum, which divides the cavity occupied by the 

 animal from that of the pedicle : they are at first comparatively small, have a rounded 

 outline, and possess the same blueish colour which the ova had in the pedicle ; but 

 as the ova advance in progress these leaves extend in every dimension, and lap over 

 each other on the back, passing through various lighter shades of colour into pale 

 pink, and finally, when ready to hatch, become nearly white (fig. 2.). These leaves 

 appear to be composed of a layer of ova irregularly placed, and imbedded in a kind 

 of parenchymatous texture, out of which they readily fall when about to hatch, on 

 its substance being torn asunder ; indeed, it appears at length to become so tender as 

 to fall entirely away, so that after the period of gestation is past, no vestige of these 

 leafy conceptacles is to be found. 



When the larvae, barely visible to the naked eye, burst forth from the ova, their 

 development goes on with such rapidity that they seem to grow sensibly while under 

 observation. These changes have been depicted in Cineras at figg. 6. 7. & 8., which 



