A Monograph on the Sub-class Cirripedia · Charles Darwin
PROTEOLEPAS BIVINCTA.
Fig. 1, Antenna of the pupa (three terminal segments of), with a portion of one of the two threads, enclosing the cement-ducts, by which the body of the Proteolepas is attached; the upper portion of the thread, and the adjoining part of the body, are represented in section. _a_, part of the great mass of cellular matter within the ovarian sack, in process of development into ova, and changing its character as soon as it enters the tube or cement-duct. _b_, membrane forming the ovarian sack and the cement-ducts, the latter enclosed within the threads of attachment. _c_, corium lining the outer membrane of the body, and the upper part of the threads. _d_, outer membrane of body. _e_, " " becoming suddenly thicker where forming the outer membrane of the thread. _e′_, outer membrane of the thread in the lower part, here not shown in section. _f_, main or second segment of the pupal antenna, the basal segment having, as in all cases, been moulted, with the carapace of the pupa. _g_, disc-segment, apparently with a small orifice for the issuing of the cement. _h_, terminal segment with the shorter spines broken off. 2, Compounded mandibular organ, sketched by the camera; _a_, supposed mandible; _b_, perhaps portion of the mandible; _c_, maxilla; _d_, ligamentous fibres giving attachment to muscles. 3, Mouth seen from the ventral side, sketched by the camera; _r_, articulation separating the mouth from the body; _c_, compounded mandibular organ; _d_, palpus, united to the opposite palpus and to the crest of the labrum; the latter forming the back of the hollow in which the compound mandibles work. 4, Diagram of the mouth of an ordinary cirripede, seen from above; _a_, outer maxilla; _b_, maxilla; _c_, mandible; _d_, labrum. 5, Diagram, illustrating the supposed changes in _position_ of the gnathites in Proteolepas, causing them to stand back to back; _a_, outer maxilla; _b_, maxilla; _c_, mandibles; _d_, labrum. _Genera_--PROTEOLEPAS AND BALANUS.
Text from Project Gutenberg, public domain in the United States.