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Updated: June 28, 2025
The pupae in both orders attach themselves by means of the adherent feet; those of the Cirripedes to rocks, shells, turtles, drift-wood, ships, etc., those of the Rhizocephala to the abdomen of Crabs, Porcellanae, and Hermit Crabs.
With species in a state of nature, every naturalist has in fact brought descent into his classification; for he includes in his lowest grade, or that of a species, the two sexes; and how enormously these sometimes differ in the most important characters, is known to every naturalist: scarcely a single fact can be predicated in common of the males and hermaphrodites of certain cirripedes, when adult, and yet no one dreams of separating them.
Protected by the abdomen of the Crab, or by the shell inhabited by the Pagurus, the parasite also no longer required the calcareous test, in which, no doubt, the first Cirripedes settling upon these Decapods rejoiced.
The Balanidae or sessile cirripedes, on the other hand, have no ovigerous frena, the eggs lying loose at the bottom of the sack, within the well-enclosed shell; but they have, in the same relative position with the frena, large, much-folded membranes, which freely communicate with the circulatory lacunae of the sack and body, and which have been considered by all naturalists to act as branchiae.
Hence we now positively know that sessile cirripedes existed during the secondary period; and these cirripedes might have been the progenitors of our many tertiary and existing species. The case most frequently insisted on by palæontologists of the apparently sudden appearance of a whole group of species, is that of the teleostean fishes, low down in the Chalk period.
It will reveal this community of descent, however much the structure of the adult may have been modified and obscured; we have seen, for instance, that cirripedes can at once be recognised by their larvæ as belonging to the great class of crustaceans.
Cichla, frontal protuberance of male. Cimetiere du Sud, Paris. Cincloramphus cruralis, large size of male. Cinclus aquaticus. Cingalese, Chinese opinion of the appearance of the. Cirripedes, complemental males of. Civilisation, effects of, upon natural selection; influence of, in the competition of nations. Clanging of geese, etc. Claparede, E., on natural selection applied to man.
Not only has this amount of elevation taken place within the period of existing Mollusca and Cirripedes; but their proportional numbers in the neighbouring sea have in most cases remained the same.
In 1846, the "Geological Observations in South America" came out, and this book was no sooner finished than Darwin set to work upon the Cirripedes.
The carapace of the Cirripedes becomes converted, as is well-known, into a peculiar test, on account of which they were formerly placed among the Mollusca, and the natatory feet grow into long cirri, which whirl nourishment towards the mouth, which is now open.
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