This last example of reef has been compared by Jukes 1 to 'a great submarine wall or terrace, fronting the whole northeast coast of Australia, resting at each end on shallow water, but rising from very great depths about the centre ; its upper surface forming a plateau covered by 10 to 30 fathoms of water, but studded all over with steep-sided block-like masses which rise up to low water-level. These masses are especially numerous, and most linear along the edge of the great bank on which they rest; the passage between them being often very narrow, like regular embrasures opened here and there through the parapet wall of a fortress. These 'individual reefs' running along the outer edge protect the comparatively shallow water inside, and with the numerous inner reefs that are scattered over its space make it one great natural harbour.' The third and last class, or 'atoll' (Fig. 3), is an elliptical, oval or roundish ring of coral, with here and there a break in its Fig. 3.-Stewart Atoll or Sikiana (lat. 8°22' S. ; long. 162°58' E.). C, Reef Channel ; F, Faule Island. continuity, and with a central lake-like expanse of water, known as the lagoon. The outside water is generally very deep, and the inside shallow ; thus off the Cocos-Keeling Atoll the 1 Manual of Geology ; p. 131 ; Voyage of H.M.S. Fly, vol. i. chap. xiii. viii PREFA TOR Y NOTE. sounding-lead, at a distance of 2,200 yards from the reefs edge, sinks to a depth of 1,200 fathoms, while the lagoon is only from two to seven fathoms deep. ' Such a basin with its deep, clear channels through the reef-affording (as many of them do) room enough for all the navies of Christendom to ride at anchor-supplies the very perfection of harbour accommodation, even though the surrounding reefs are so low that during storms the breakers outside will dash over the massed wall of coral. In this lagoon marine animals of all sorts-including fishes, and pre-eminently sharks-swarm : but it is seldom that the wind disturbs the water with its smooth, glassy expanse, and curiously enough the openings in the reef are always on the leeward side, that is, in the one least exposed to the prevailing winds, so that while a ship has no difficulty in getting out to sea, it sometimes happens that it does not find an escape from the storm so easy. 5 The commonest localities for atolls are the Indian and Pacific Oceans. Stewart's atoll (Fig. 3) in the Solomon Islands, and the Menschikoff Island may be taken as typical examples. ' a true coral-reef.' ' No other work of mine, 5 he says, 1 ' was

Population genetic evidence suggests differentiation among evolutionarily significant units of southern and northern Appalachian brook trout, with the zone of contact in southwestern Virginia. Before this differentiation was recognized, brook trout of northern origin were stocked throughout the southeastern United States. In order to determine this differentiation, established allozyme markers were used to classify 56 southwest Virginia populations as southern, northern, or introgressed. Variation at 4 polymorphic loci, including the diagnostic creatine kinase (CK-A2*) locus, indicated that 19 populations were of southern origin, 5 of northern origin, and 32 of mixed genetic origin. Data compiled among genetic studies of brook trout in the southern Appalachians showed that the southern/northern break is sharp, occurring at the New/Roanoke-James watershed divide. New River drainage populations exhibited the southern allele at high frequency, suggesting their historic native character as southern, with presence of northern alleles due to stocking or stream capture events. In conclusion, the present study suggests that management of southern Appalachian brook trout should include: (1) genetically cognizant planning of stocking events, (2) management of populations on a stream-by-stream basis, (3) prioritized conservation of pure southern brook trout populations, and (4) use of southern Appalachian hatchery stocks in restoration efforts.

Cation−π interactions play a significant role in the stabilization of globular proteins. However, their role in collagen triple helices is less well understood and they have rarely been used in de novo designed collagen mimetic systems. In this study, we analyze the stabilizing and destabilizing effects in pairwise amino acid interactions between cationic and aromatic residues in both axial and lateral sequential relationships. Thermal unfolding experiments demonstrated that only axial pairs are stabilizing, while the lateral pairs are uniformly destabilizing. Molecular dynamics simulations show that pairs with an axial relationship can achieve a near-ideal interaction distance, but pairs in a lateral relationship do not. Arginine−π systems were found to be more stabilizing than lysine−π and histidine−π. Arginine−π interactions were then studied in more chemically diverse ABCtype heterotrimeric helices, where arginine−tyrosine pairs were found to form the best helix. This work helps elucidate the role of cation−π interactions in triple helices and illustrates their utility in designing collagen mimetic peptides.

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