A Monograph on the Sub-class Cirripedia (Volume 2 of 2) / The Balanidæ, (or Sessile Cirripedes); the Verrucidæ, etc., etc.

by Charles Darwin

• [13], Lateral view of the posterior extremity of the thorax, much enlarged, with its articulated appendages represented only on one side; the four thoracic segments, l, m, n, o, correspond with those represented in fig. 5. In one monstrous specimen, segment n, bore a single cirrus. The posterior thoracic segment, o, bearing the sixth pair of cirri, o′, is very small and obscure, and can be seen only by separating the fifth and sixth pairs of cirri; or by longitudinally bisecting the thorax, and viewing the inner side; n′, fifth cirrus; a, lower segment, b, upper segment of pedicel; c, lower, and d, upper segment of the one ramus, the other ramus being represented by the coriaceous boss c′; o′, sixth cirrus, with similar segments; p, caudal appendage.
• [14], First cirrus.
• [15], Maxillæ, with the lower end of the apodeme cut off, showing the curious membranous swelling on the side towards the mandible.

PLATE [23.]
Genera—[ALCIPPE] AND [CRYPTOPHIALUS].

[ALCIPPE LAMPAS.]

• Fig. [16], Pupa of [male Alcippe lampas], viewed laterally; a, antennæ, c′, eyes attached to the apodemes; above these the single eye of the mature male may be distinguished.
• [17], Abdomen of the same; p, posterior end of thorax; q, abdomen; r, caudal appendages.
• [18], [Male of Alcippe lampas] immediately after the metamorphosis, the ventral surface being uppermost, but the specimen has been in some way distorted, as the lobe (i) ought to project on the opposite side; a, antennæ of the pupa; g, h, lateral lobes; internal organs not yet formed; orifice at upper end (i) not visible; scale same as for the pupa, fig. 16.
• [19], [Male of Alcippe lampas], when fully mature; scale same as in last figure (18) and as in fig. 16.
• a, antennæ of pupa.
• b, vesicula seminalis.
• c, eye, (seen in fig. 16 above the eyes of the pupa, c′.)
• d, testis.
• e, lower transverse muscle.
• f, upper transverse muscle.
• g, h, lateral lobes of the external covering, answering to the sides of the peduncle of the female.
• i, terminal lobe on the ventral side of the orifice, probably corresponding with a in fig. 1, Pl. 22.
• k, orifice of the tubular sack.
• l, oblique muscles on the ventral side of the sack.
• m, probosciformed penis, shown exserted; m′ portion within the tubular sack.

[CRYPTOPHIALUS MINUTUS.]

• Fig. [1], [Cryptophialus minutus] (female with an attached male) viewed
  laterally, but with the disc (H) rather turned towards the beholder, much enlarged; a, orifice leading into the sack; H, thin horny disc by which the animal is attached within its cavity; H′, upper free worn edge of the disc; z, male attached in its usual position to the edge of the disc of the female.
• [2], [Cryptophialus minutus], natural size, within a half-inch circle; this represents the largest specimen which I have ever seen.
• [3], Half the orifice, with a large portion of the external membrane and of the membrane lining the sack.
• a, a, dentated horny rim of orifice.
• b, b, external membrane, with the underlying corium or true skin removed.
• b′, a horny bar, expanding at its lower end into a toothed plate, and at the upper end connected with the horny rim round the orifice.
• c, c, membrane lining the sack.
• c′, horny bar by which this membrane is strengthened.
• c′′, thickened membrane, or bar, expanding into fibrous sheets for the attachment of a muscle.
• d, delicate lateral lip, within the outer dentated horny rim.
• [4], Orifice of sack, cut off, widely open, viewed from above; a, horny dentated rim; b′, top of horny bar, where united to the rim; d, inner lateral lip folded backward; d′, lip, with coarser hairs, at the carinal end of the orifice.
• [5], Animal with the outer tunics removed, viewed laterally.
• a, dentated horny rim of orifice, continuous with
• b, outer membrane, here cut off.
• c, inner membrane of sack, continuous with
• c, c, the reflexed membrane of the body, by which the body is united to the disc and outer envelopes.
• e, lancet-shaped labrum.
• e′, projection behind the labrum.
• f, palpi.
• g, outer maxillæ, between which and the palpi lie the inner maxillæ and mandibles; these latter are rather exaggerated in size.
• h, first maxilliped, in a rudimentary condition, close above which is the articulation separating the whole mouth (o) from the first (¹) segment of the body.
• i, k, tapering appendages springing from the second and third segments of the body.
• l, pedicels of the three pairs of abdominal cirri.
• m, cirri, three pairs of.
• o, mouth, of great size, formed by the confluence of the lower segments of the gnathites.

• ¹, first segment of body, homologically the last or seventh cephalic segment.
• ², second segment of body, homologically the first thoracic segment.
• ³, third segment of body, homologically the second thoracic segment.
• ⁴, fourth segment of body, homologically the third thoracic segment.
• ⁵, fifth segment of body, homologically the fourth thoracic segment.
• ⁶, sixth segment of body, homologically the fifth thoracic segment.
• ⁷, seventh segment of body, homologically the sixth thoracic segment.
• ⁸, eighth segment of the body, homologically the seventh thoracic segment.
• [6], Front of mouth; g, outer maxillæ; g′, an articulation separating the mouth from the membrane of the first segment of the body; h, first pair of maxillipeds; whole figure on same scale with the labrum, fig. 9.
• [7], Maxillæ, drawn on thrice the scale as the outer maxillæ; a, apodeme.
• [8], Mandibles, drawn on thrice the scale as the outer maxillæ.
• [9], Labrum, on same scale with the outer maxillæ, fig. 6, and one third of the scale of the mandibles and inner maxillæ; e, labrum; f, palpi.