I. CRUSTACEA: CIRRIPEDIA 



373 



with few exceptions, in contrast to most other arthropods, are hermaphro- 

 ditic, a condition possibly correlated with their sedentary life and the con- 

 sequent need of self-impregnation. The testes lie in the sides of the body; 

 the ovaries in the Lepadids are in the stalk, in the Balanids in the basal 

 plate. In cases of several solitary hemaphrodite species complementary 

 dwarf males occur. These are very small, purely male forms, with ex- 

 tremely simple structure (fig. 392), which live inside the mantle cavity near 

 the genital openings. The unsegmented body is enclosed in a sac (a 



B 



FIG. 392. FIG. 393. 



FIG. 392. Male of ALcippe lampas. an, antenna; /, mantle lobes, m, muscles; oc, 

 ocellus; p, penis; t, testis; vs, seminal vesicle. 



FIG. 393. Nauplius (.4) and Cypris (B) stages of Sacculina carcini. (after Delage). 

 i, 2, antennae; 3, mandible; /, cirrous feet; m, muscles; oc, nauplius eye; ov, anlage 

 of ovary. 



soft-skinned shell), and anchored by the antenna?. The long penis pro- 

 trudes from the mantle. In the genus Scalpellum there are purely her- 

 maphroditic species, hermaphroditic species with complemental males, 

 and purely dioecious species. 



Since the hard shells of the barnacles resemble those of the molluscs, it is 

 not to be wondered that these forms were long regarded as belonging to that 

 group. It was not until the development (fig. 393) was studied that the error 

 was corrected. A large nauplius comes from the egg and later is metamorphosed 

 into a second larval stage with bivalve shell which, from its appearance, is 

 called the cypris-stage. This becomes fixed and develops into the adult, losing 

 the compound eyes and retaining the nauplius eye. 



Order I. Lepadidae. 



Stalked cirripeds, with shell largely formed of scuta, terga, and carina; 

 other parts may be added. Lepas anatifcra* (fig. 115), the goose barnacle, o\\rs 

 its common name to a mediaeval myth which claimed that the Irish (or bernicle) 

 goose developed from these animals. Anelasma squalicola, thin-skinned, 

 parasitic on sharks, forms a transition to the Rhizocephala. 



