CRUSTACEA. 
267 
and We believe that if Prof. Claus had waited until the embryo 
that he tore from the ovum had completed its period of egg- 
life, he Would have found the same; for there is little that 
appears inconsistent in his embryo being the immature stage of a 
specimen similar to that which we possess of the Phyllosoma 
form of the P«/mM?'M5-larva *. 
He also describes the larva of an anomurous Crustacean (Tlhi* 
zostoma cruciatum, Less.), and points out its general resemblance 
to the Zoea of the Prawns. In fact, the larva of the anomu- 
rous Crustacea is an intermediate form, resembling the Zoea of 
the Brachyura in the cephalon, and that of the Macrura in the 
pleon; but though this condition be preserved during a great 
portion of the periods of growth, yet the near general resem- 
blance of the young hermit-crab to that of the macrurous 
Crustacea is so very considerable that it has been taken as the 
type of a genus by Prof. Milne-Edwards, and described as such 
under the name of Glaucothoe perhnii (Ann. des Sc. Nat., March 
1830). This pretty little creature not only carries four anterior 
pairs of pleopoda as long swimming-appendages, but has the 
dorsal surface of the pleon protected by erustaceous plates, and 
likewise has the posterior pair of pleopoda equilaterally developed, 
all of which conditions it loses upon taking upon itself the 
habits of its race, that of residing in a shell of a mollusk. They 
then cease to exist as free swimmers in the sea, and sink to 
the bottom and crawl out their existence. 
We cannot forbear at this place from noticing the very great 
alterations from the normal conditions of a crab, which must 
take place in the progressive development of Hypoconcha sabu- 
losa (Guerin-Meneville, Revue et Magasin de Zoologie, No. 6, 
1854) = Cancer sabulosus (Herbst, Naturgeschichte der Krabben, 
pi. 48. f. 2, 3), Avhieh genus, like P«^wr?/.9, inhabits the shell of a 
mollusk, preferring a single shell of a bivalve mollusk to that of 
a spiral univalve. The consequence is that the whole dorsal 
surface is so far covered that neither the organs of vision nor 
the antennae could be of any use in their ordinary position ; 
they are consequently inverted, and produced on the ventral 
surface. 
VlII. In this division Dr. Muller discusses the development 
of the Edriophthalmous Crustacea, and compares the affinity 
and divergence of the several forms, particularly of the para- 
sitical family of Bopyridse, the adult females of which diverge 
to so large a degree, that iii Ento7iiscus and Cryptoniscus they 
would, but for the character of their larvae, be mistaken for 
Planariae or Ann elides. 
In this chapter he mentions and figures the first two gnatho- 
^ The figure given in the ‘ Dublin Nat. Hist. Review ’ is a poor represen- 
tation of the true animal, which only distantly resembles, rather than repre- 
sents the form of the genus Phyllosoma. 
