168 W. Lilljeborg on the Genera Peltogaster and Liriope. 
larvee in the lateral apophyses of the anterior part of the body ; 
and as the mouth is situated in this organ, it appears that it also 
has been formed by the transformation of the tubular mouth of 
the larva. It presents different forms in the different species, 
and may furnish distinctive characters. Where-it is fixed, the 
epidermis is always firmer and thicker, and it sometimes even 
extends over the epidermis like a shield (fig. 8b). Sometimes 
there is only a ring of firmer tissue on the epidermis round its 
base. When the Peltogastri which have the organ of adhesion 
rounded, and not ramose, are separated from the skin of the 
Pagurus, the latter exhibits a round hole at the point where 
the organ of adhesion was fixed; through this aperture they no 
doubt suck their nourishment. 
The newly-hatched larva (fig. 16) is less elongated than the 
larvee of other Cirripedes. The posterior part of the body is not 
pointed, but rounded and obtuse, as in the larve of the Lerneide 
and Copepoda. But the larva of Peltogaster differs from the 
latter by an apophysis projecting from each side of the front of 
the body, and issuing from the lower surface. In the very 
young larvee this is attached to the body in such a manner that 
it is difficult to see it; but as the second pair of antenne are 
formed in these apophyses, and it is with these that the Cirri- 
pede afterwards adheres, it is evident that the apophyses are of 
the greatest importance, and their presence may be regarded 
as characterizing the animal. The larve of Cirripedes are 
distinguished from those of the Lernzidze and Copepoda by the 
early presence of the first pair of antennz not in the form of 
legs. The author has been unable to discover these antennz in 
newly-hatched larvze or in those still contained in the eggs*. 
No specimen of this genus has hitherto been discovered ex- 
cept upon species of the genus Pagurus. They are usually fixed 
upon the left side of the abdomen, in such a way that the aper- 
ture leading into the cavity of the body is turned towards the 
anterior part of the Pagurus, and consequently towards the 
aperture of the shell in which the Pagurus resides. This is pro- 
bably to enable the young to escape as rapidly as possible. The 
* According to Claus (Archiv fiir Naturg. 1858, p. 1, and “ Ueber den 
Bau und die Entwickelung parasitischer Crustaceen,”’ Cassel, 1858, p. 5), 
the parts of the mouth in the Copepoda are formed from the third pair of 
feet of the larvee, and the antennz from the first and second pairs. As, 
according to Darwin, the feet in the larvae of the Cirripedes have no sig- 
nificance as future antenne, the appendages of the mouth of the Cirri- 
pedes, by analogy with the order of development of parts in the Copepoda, 
should be formed from the first pair of feet of their larve. But Darwin 
thinks that this pair of feet corresponds with the second pair of feet or 
cirri in the developed animals. There is here, at any rate, a great difference 
in the development of the Cirripedia and Entomostraca. 
