216 



CRUSTACEA. 



the adult Cirripede, the third Nauplius limb as well as the second 

 being supposed to vanish completely. In the more posterior section 

 of the body, we find six pairs of swimming limbs (rf), which, in 

 their structure, strikingly recall the thoracic limbs of the Copepoda, 

 and are also similarly used as swimming feet. Each of these consists 

 of a two-jointed basal segment provided with an exopodite and endo- 

 podite, each of these, again, being composed of two joints and clothed 

 with long swimming setae. Posteriorly, the body terminates in a 

 short abdomen (ab) composed of four segments, the last of which 

 ends in two furcal appendages bearing long setae. 



With regard to the internal organs, it should be mentioned that, at this stage, 

 sac-like outgrowths of that enlargement of the intestinal canal which is called 

 the stomach begin to appear : these develop into the so-called liver ; further, 

 that the rudiment of the ovaries is to be seen in the shape of paired tubes 

 situated ventrally in the cephalic region. 



Fio. 105.— Pupa of Lepas pectinata (after Claus, from Lang's Text-book), iia, Nauplius eye ; 

 pa, paired eye ; rf, thoracic limbs (with the tendril-like— cirriform— feet beginning to form 

 inside) ; o, mouth ; d, intestine ; L, liver ; sm, adductor muscle ; sc, scutum ; t, tergum ; ca, 

 carina ; cd, cement-gland ; I, first antenna with the sucking disc. 



The free-swimming Cypris-like larva, after becoming finally 

 attached, gives rise to the fixed Cypris-Wie larva (Fig. 105) of 

 the Cirripedia. As, at this stage, the larva ceases to feed and 

 loses all power of locomotion, while important external and internal 

 changes are going on in the body beneath the cuticle of the Cypris 

 stage (as if beneath a pupal integument), this stage has been well 

 called the pupal stage (Cy pis-like pupa). From this, by the casting 

 of the cuticle of the Cypris-like stage, proceeds the young 

 Cirripede. For details as to the processes through which these 

 transformations are brought about, we are indebted chiefly to the 



