MOUTH-PARTS OF THE CYPEIS-STAGB OF BALANUS. 271 



lip or to the mandible ; the two hinder pairs Claus describes 

 as giving the impression of a single pair of appendages. 



Of the two species of Balanus the Cypris-stage of which I 

 have carefully examined^ B. perforata s, on account of its 

 minute size, is much less favourable for purposes of investiga- 

 tion than B. balanoides. Repeated dissections of the pupa 

 of the latter form have enabled me to form a tolerably good 

 idea of the constitution of the buccal mass. 



Viewed from behind (fig. 3), a pair of appendages (mx^.), 

 clearly identical in position and relations with the lower lip, or 

 second pair of maxillae of the adult, is recognisable. These 

 are attached on each side behind along an oblique straight 

 line, and are somewhat broader at the base than at the apex. 

 Like the second maxillae of the adult, they are closely applied 

 to one another in the middle line. Seen in side-view (fig. 8) 

 they are somewhat lanceolate in shape, the apex generally 

 projecting somewhat forwards ; the hinder margin is convex, 

 while the anterior is somewhat sinuous. Like the remaining 

 mouth-parts, and like those of Lepas, as described by Pagen- 

 stecher, they are simple lobes devoid of teeth or bristles. At 

 the junction of these appendages with the first pair of maxillae 

 may be seen a conical chitinous process (figs. 1^ 3, 4, 6). 



The first maxillae {?nw^.) are situated externally to the 

 second, and project somewhat behind the latter (fig. 1, cf. also 

 fig. 11). They are similarly convex externally^ but are simply 

 concave on the inner side ; they lie in planes inclined outwards 

 at a greater angle than the second maxillae (cf. fig. 11). Like 

 the remaining mouth-parts they are broadest externally, 

 narrowing towards the centre. They do not attain quite the 

 vertical height of the second maxillae (fig. 1), 



The mandibles are large, and occupy the outer part of the 

 buccal mass (figs. 1 — 3), being found externally and anteriorly 

 to the first pair of maxillae (figs. 1 — 3; cf. also fig. 11). The 

 main portion of the mandible passes distally into an inwardly- 

 curved process with a somewhat truncated end, giving the appen- 

 dage much the form of the adult mandible or first maxilla 

 though, as already remarked, no teeth or hairs are present. 



