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

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

Chapter 282: PLATE 29. CIRRI AND LARVÆ, FIRST STAGES.
By Charles Darwin
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This work presents a detailed monograph on the sub-class Cirripedia, focusing on various species of barnacles, including the Balanidæ and Verrucidæ. It includes comprehensive descriptions, classifications, and illustrations of these organisms, contributing to the understanding of their biology and taxonomy. The author examines their anatomical features, reproductive habits, and ecological roles, providing insights into their adaptation and evolution. The text serves as a significant resource for naturalists and biologists interested in crustacean studies, reflecting the author's meticulous research and dedication to the field.

PLATE 29.
CIRRI AND LARVÆ, FIRST STAGES.

  • Fig. 1, Sixth cirrus of Balanus amphitrite (var. cirratus), showing
    the muscles.
  • a, b, flexor and extensor muscles, moving the upper segment (i to k) of the pedicel.

  • c and d, flexor and extensor muscles, apparently moving the lower segments of both rami, as a whole; the lower articulations in these rami being confluent.
  • e and f, flexor and extensor muscles extending up both rami (those only in the near ramus being figured) to their tips.
  • g g, flexors of the separate segments in both rami.
  • h, basal articulation of lower segment of the pedicel.
  • i, upper articulation of lower segment of the pedicel.
  • k, upper articulation of upper segment of pedicel.
  • 2, Fourth cirrus of Acasta sulcata.
  • i, upper articulation of the lower segment of pedicel.}These two letters apply to all the figures, 1 to 6.
  • k, upper articulation of the upper segment of pedicel.}
  • l, curved teeth on the pedicel.
  • m,””on the segments of the anterior ramus.
  • 3, Third cirrus of Chthamalus antennatus.
  • 4, Second cirrus of Balanus perforatus, viewed exteriorly and laterally.
  • 5, Third cirrus of Xenobalanus globicipitis.
  • 6, Sixth”””
  • 7, Spermatozoa (copied from Mr. C. Spence Bate, in ‘Annals and Mag. of Natural History’ (S. 2), vol. viii, Pl. VIII).
  • a, of Verruca Strömia, in an early condition.
  • b, of Balanus balanoides, more mature.
  • c, of Balanus perforatus, apparently mature.
  • 8, Larva of Scalpellum vulgare, immediately after coming out of the egg, seen on the ventral surface (letters of reference given below).
  • 9, Larva of Balanus balanoides, immediately after coming out of the egg, seen on the ventral surface, copied from Mr. C. Spence Bate’s drawing in ‘Annals and Magazine of Natural History’ (S. 2), vol. viii, Plate VI, fig. 1 (letters of reference given below).
  • 10, Larva of Chthamalus stellatus, after the first moult, but during the first stage, seen on the ventral surface, copied; with some alterations, from Mr. C. Spence Bate’s drawing in ‘Annals and Magazine of Natural History’ (2 Ser.), vol. viii, Plate VIII, fig. 13.
  • (The following letters apply to above figs. 8, 9, 10.)
  • a, eye.
  • b, first pair of antennæ, not observed in fig. 9.
  • b′, the same antennæ, as yet encased (in fig. 8) within small horns.
  • c, horns, including the second pair of antennæ.
  • d, mouth, probosciformed: in fig. 8, the specimen having been acted on by potash, the œsophagus can be seen within, with the orifice beneath the swelling, which latter perhaps answers to the labrum.
  • e, first, uniramous natatory leg (homologically the second thoracic limb).

  • f g, second and third, biramous natatory legs (homologically the third and fourth thoracic limbs.)
  • h, posterior point of carapace.
  • i, forked terminal projection of the body or abdomen.
  • l, second forked projection.
  • m, two sharp points, apparently representing a third forked projection.
  • n, a rounded swelling, apparently lying between the carapace and the supposed abdomen, and believed to form the anus.