ANATOMY OF THE BARNACLE. 



273 



Fig. 222. A barnacle. Balanus 

 ., porcatus. Natural size. 



(Fig. 222), a shell-like animal, the shell composed of several 

 pieces, with a multivalvc, conical movable lid, having an 

 opening through which several pairs of long, many-joint- 

 ed, hairy appendages are thrust, 

 thus creating a current which sets 

 in towards the mouth. The com- 

 mon barnacle (Balanus balanoi- 

 des Stimpson) abounds on every 

 rocky shore from extreme high- 

 water mark to deep water, and 

 the student can, by putting a 

 group of them in sea-water, ob- 

 serve the opening and shutting 

 of the valves and the movements 

 of the appendages or "cirri. 



The structure of the barnacle may best be observed in 

 dissecting a goose barnacle (Lepas fascicularis Ellis and 

 Solander, Fig. 223). This barnacle consists of a body (capit- 

 ulum) and leathery peduncle. There are six pairs of jointed 

 feet, representing the feet of the Cycles (Fig. 231). The 

 mouth, with the upper lip mandibles (B, 1), and two pairs 

 of maxillae, will be found in the middle of the shell. A 

 short oesophagus (according to J. S. Kingsley, whose ac- 

 count we are using) leads to a pouch-like stomach and tubular 

 intestine. This form, like most barnacles, is hermaphroditic, 

 the ovary (A, o)lying at the bottom of the shell, or in the 

 peclunculated forms in the base of the peduncle, while the 

 male gland (t) is either close to or some distance from the 

 ovary. There is also at the base of the shell, or in the pe- 

 duncle when developed, a cement-gland, the secretion of 

 which is for the purpose of attaching the barnacle to some 

 rock or weed. 



While the sexes are generally united in the same indi- 

 vidual, ir the genera INa (Fig. 224) and Scalpellum (Figs. 

 225, 226, besides the normal hermaphroditic form, there 

 are females, and also males called "complementary males," 

 which are attached parasitically both to the females and 

 the hermaphroditic forms, living just within the valves or 

 fastened to the membranes of the body. These comple- 



