•34 



THE CRUSTACEA 



the crab's abdomen in a position inaccessible to the larva. As a 

 rule, the crab is attacked when the integument is still soft after 

 ecdysis, and the larvae may attach themselves at any point on the 

 dorsal surface of the carapace or on the limbs, at the base of one of 

 the large setae where the articular ring of uncalcified cuticle allows 



Fig. n'J. 



Larval stages of Saccnlina carcini. A, naiiplius after the first moult. B, free-swiiiiniinH 

 Cypris-stAge. C, t'l/iJns-stage after attachment to a seta (6/)) of the host. D, formation of the 

 Kentrogon larva. E, Kentrogon-Htnge, after the Ci/^rris shell has been cast off and the "dart" 

 lias been formed. F, penetration of the dart through the cuticle of the host. 1, 2, 3, the three 

 jiairs of nauplius-limbs. I-VI, thoracic limbs, ah, abdomen; hb, seta of the host; /,' fat- 

 globules ; f.s, frontal sense-organ ; gl, glands of the antero-lateral horns ; ov, mass of mesoderm 

 cells regarded by Delage as the rudiment of the ovary ; }'/, " dart " ; va, nauplius-eye. ' (After 

 Delage, from Korschelt and Ueider's Einhryulogy.) 



more easy penetration (Fig. 82, C). Only one of the antennules 

 is used for attachment, the filamentous process of the terminal 

 segment clasping the base of the hair. The whole of the thoracic 

 region of the lar^a, Avith its appendages and muscles, now becomes 

 detached and is thrown off, and later the bivalve shell is also 

 shed, while the contents of the anterior region of the body become 



