206 



NATURAL HISTOJtY. 



from the adult than in others of the long-tailed Crustacea. They are, however, sufficiently important 

 to mention (Fig. 23). The eyes of the young Lobster are sessile, not mounted upon eye-stalks. 

 The long antennae are not seen, nor the beak or rostrum. The thoracic feet are rudimentary. The 

 abdominal feet are entirely absent, as in the young Crab. At a later moult the jointed thoracic 



limbs are seen, and the antennae begin to be 

 developed. The hind body, or abdomen, is, 

 however, still without appendages, and the 

 eyes without eye-stalks. Still later these ab- 

 dominal feet make their appearance. 



In estimating the greater or less extent of 

 metamorphosis undergone by the young of any 

 Crustacean in its passage to the adult animal, 

 it is necessary also to take account of its embry- 

 onic development, for many species, both of 

 the Podophtkalmia (or stalk-eyed) 

 and Edriophthalmia (or sessile-eyed) 

 Crustacea undergo these larval 

 changes in the egg, whilst others (as 

 Asellus and My sis) do so in the incu- 

 batory pouch of the mother. 



The Norway Lobster (Nepbropt 

 norvegicus, Fig. 24) occurs on both 

 the English and French coast, as well as on that of 

 Norway, and extends as far south as the Mediterra- 



Fig. 23. YOUNG LOBSTERS. 



1, z'va just born: 2, after first moult. 



nean. The body of this elegant species is long, and the 

 segments extremely cylindrical in form ; the cephalo- 

 thorax is compressed at the sides. The great claws are 

 long, slender, spiny, and ridged strongly down the centre ; 

 the rostrum is long and slender. The scale at the 

 outer base of the antennae is large. The eyes are 

 large and prominent. The colour of this Lobster is 

 much paler than that of Homarus, and there are bands 

 of darker colour on the body-rings. There is only one 

 species known. 



The Common River Cray-fish (Astacusfluviatilis}, 

 a fresh-water genus, was separated by Milne-Edwards 

 from the Lobsters, and may be readily known from 

 others by the rostrum or beak having a small tooth 011 

 each side. Its carapace is granulated, and the telson, or 

 median plate of the tail, is divided half-way up by a 

 transverse joint across it, as are also the outer side- 

 lobes of the tail. The outer antennae have the second 

 and third joints roundish, and covered by a broad and 

 movable scale, which is narrowed towards each ex- 

 tremity, and pointed. The last joint or ring of the 

 thorax is movable, whereas in the common Lobster the 

 last thoracic ring is firmly adherent to the rest. The 

 exopodite of the antennae is reduced to a mere scale. All 

 the abdominal appendages are well developed in both 

 sexes, and in the males the two anterior pairs are some- 

 what like those of the male of Homarus, but less modified. Fig. 24. NORWAY LOBSTER (Kephrops 



