1 82 THE FLOATING ANIMALS 



of limbs (Figs. 120, 121). This larval stage moults or 

 sheds its skin repeatedly, not only growing, but also 

 changing its shape somewhat at each moult, until it 

 attains the parent form. 



Many of the higher Crustacea, after passing through 

 the Nauplius stage, gradually attain a Zoea stage, 

 which may be recognized by the limbs of the fore-part 

 of the body having sprouted, by a pair of large eyes 

 having appeared, and by the tail part of the body 

 having grown out ; the latter carries no limbs, 

 except sometimes the last pair (Figs. 122-124). 



A few families have special larvae, which are often 

 common near shore after the breeding season. Thus 

 the crawfish, or spiny lobster (Palinurus), passes 

 through the remarkable stage Phyllosoma (Fig. 128) ; 

 the crabs, after their zoea stage, assume the form 

 known as Megalopa before tucking in their tails 

 (Fig. 127) ; and the Stomatopoda have a set of larvae 

 peculiar to themselves (Fig. 125, 126). 



Of the group to which oysters, snails, and cuttle-fish 

 belong, the Mollusea,some subdivisions occur in Plankton. 



The oyster-forms, or Lamellibranchs, possessing two 

 shells, are occasionally represented by larvae (Fig. 134). 

 The snail-forms, or Gastropoda, are frequently met. 

 Janthina, a warm-water snail, sometimes thrown on 

 our western shores, has a purple shell ; to its foot is 

 attached a raft, on the underside of which the eggs are 

 embedded. Atlanta (Fig. 131) has a spiral shell, with a 

 narrow keel ; Carinaria, like a transparent slug, carries 

 a shell on its hump (Fig. 132) ; very like it, but without 

 shell or hump, are several other warm-water forms. 

 The pteropod, or " wing-footed " forms, are found in all 

 seas ; of these the majority have shells (Figs. 133, 135). 

 Near-shore larvae of Gastropods are often plentiful; 

 the most characteristic is the " Veliger " stage (Fig. 136) . 



