Conger punctus See Eelpouts

Constancy Lack of change, here discussed by CD with reference to the evolution of repetitive patterns in body parts: Whenever any part or organ is repeated many times over in the structure of a species, it is variable in number, the same part or organ becoming numerically constant, either in other parts of the body of the same individual, or in other species, whenever the number is few [...Inbirds, it] might be thought that the greater importance of the wing and tail feathers would account for their constancy; but I doubt this, for we find the same rule in the vertebrae, which are generally constant in mammals & birds, but in snakes, according to Schlegel, the number varies greatly in the same species. So I believe it is in the teeth of fish & reptiles compared with the teeth of mammals. (Big Species Book, p. 567; Schlegel 1843, p.27).

Coquimbo City in Chile where CD collected the following species, described by Jenyns: Umbrina ophicephala (Fish, p. 45; see Croakers); Blennechis ornatus (Fish, p. 85; Fish in Spirits, no. 1211; see Blennies); and Clinus crinitus (p. 90; C. crinitis in the index of Fish; see Blennies).

Coral Reefs Short title of "The Geology of the Voyage of H.M.S. Beagle. Part 1. Structure and distribution of Coral Reefs" (Darwin 1842), in which CD presented his revolutionary (and now widely accepted) theory linking the subsidence of land and coral reef formation, formulated before [he] had ever seen a true coral reef (Autobiography, p. 97, Stoddart 1962,1994; see also Cocos Islands).

The key point of the theory in Coral Reefs is that, while individual corals will rapidly settle on the rocks around the emerging, usually conical tip of new volcanic islands, or along emerging coastlines, these structures need to slowly sink for substantial reefs to develop on them. Given subsidence, 'fringing' reefs will be the first to be formed. As volcanic islands sink deeper, and the coral reefs along their coastline grow upward to stay within the lighted zone, atolls (with their internal *lagoons) may then be formed, whose roundish shape reflects their having been formed on top of a cone. Or as put by CD when he began to flesh out the theory later articulated in Coral Reefs: In time, the central land would sink benath the level ofthe sea & disappear, but the coral would have completed its circular wall (Diary, April 12, 1836). Also, repeated sea-level changes may gradually shift the locations of fringing reefs away from a coastline, thus forming barrier reefs (such as occur offeastern Australia, and Belize).

Among other things, this theory implies that if an island sinks so fast that coral growth cannot keep up, then its reefs will 'drown.' It is thus appropriate to use the *eponym 'Darwin Point' for the combination of lowest temperature and light (i.e. the highest latitude) at which coral growth can still compensate for subsidence (Grigg 1982).

These concepts will become increasingly better known to the public in the next decades, as increased numbers of bleaching events (due to increasing water temperature and possibly other anthropogenic stresses), and increased coastal turbidity (also anthropogenic) will reduce the ability of coral reefs to match sea-level increases.

Covington, Syms

Coral Reefs provided material for only two entries in this book, on *parrotfishes, and the effect of strong rain on *Cocos Islands reef fishes.

Cormorants Fish-eating birds of the genus Pha-lacrocorax, of which one species is described in *Birds (p. 145), based on a specimen from *Patag-onia, though without the behavioural observation that CD added to most of John Gould's morphological accounts.

This was the Imperial shag Phalocrocorax atri-ceps (P. carunculatus in Birds), previously treated as a complex of species, but now considered a single species with variable plumage, and a wide distribution that includes both Patagonia and the *Falkland Islands (Harrison 1987, p. 230). Hence, we can now assign to that species the field observations CD made at Berkeley Sound, East Falkland Islands, where he [s]aw a Cormorant catch a fish and let it go 8 times successively like a cat does a mouse or *otter a fish (Notebook 1.14;March 21,1833,cited in Armstrong 1992a, p. 104;Armstrong 1993a).

Correspondence Short title of the Correspondence of Charles Darwin, published since 1985 by Cambridge University Press, in a series of volumes with varying combinations of the same group of(associate) editors.

Twelve volumes were available as source of material for this book: 1 (1821-36; Burkhardt et al. 1985b); 2 (1837-43; Burkhardt et al. 1986); 3 (1844-46; Burkhardt et al. 1987), 4 (1847-50; Burkhardt and Smith 1988); 5 (1851-5; Burkhardtand Smith 1989); 6 (18567; Burkhardt and Smith 1990); 7 (1858-9, + supplement for 1821-57; Burkhardt et al. 1991); 8 (1860; Burkhardt etal. 1993), 9 (1861; Burkhardt et al. 1994), 10 (1862; Burkhardt etal. 1997), 11 (1863; Burkhardt etal. 1999), and 12 (1864; Burkhardt et al. 2001; the only volume not to contain anything by CD on fish).

Once fully published, the Correspondence will present the text of all letters still extant (about half of all; Browne 2002, p. 11) that were written by CD, or received by him, a total of about 14 000 items (all briefly documented in the *Calendar of Burkhardt et al. (1985a), used here to infer the contents of letters so far unpublished). Also, these magnificent volumes include biographic notes, bibliographies and other material documenting the work and impact ofCD.

Previous compilations of CD's correspondence existed, notably by his son Francis (Darwin 1887; Darwin and Seward 1903; see also Autobiography), meant to cover the entire range of his work through a selection of (heavily expurgated) letters. Other compilations document his interactions with various individuals, e.g. his mentor J. S. *Henslow (Barlow 1967), or the marine biologist A. *Dohrn (Groeben 1982). The Correspondence supersedes these previous efforts, which in any case did not exhibit the same, extremely high standard ofscholarship.

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