Line	Critics maintain that the fiction of Herman Melville
	(1819–1891) has limitations, such as its lack
	of inventive plots after Moby-Dick (1851) and its
	occasionally inscrutable style. A more serious, yet
(5)	problematic, charge is that Melville is a deficient
	writer because he is not a practitioner of the “art of
	fiction,” as critics have conceived of this art since the
	late nineteenth-century essays and novels of Henry
	James. Indeed, most twentieth-century commentators
(10)	regard Melville not as a novelist but as a writer of
	romance, since they believe that Melville’s fiction
	lacks the continuity that James viewed as essential
	to a novel: the continuity between what characters
	feel or think and what they do, and the continuity
(15)	between characters’ fates and their pasts or original
	social classes. Critics argue that only Pierre (1852),
	because of its subject and its characters, is close to
	being a novel in the Jamesian sense.
	However, although Melville is not a Jamesian
(20)	novelist, he is not therefore a deficient writer. A more
	reasonable position is that Melville is a different
	kind of writer, who held, and should be judged
	by, presuppositions about fiction that are quite
	different from James’s. It is true that Melville wrote
(25)	“romances”; however, these are not the escapist
	fictions this word often implies, but fictions that
	range freely among very unusual or intense human
	experiences. Melville portrayed such experiences
	because he believed these best enabled him to
(30)	explore moral questions, an exploration he assumed
	was the ultimate purpose of fiction. He was content
	to sacrifice continuity or even credibility as long
	as he could establish a significant moral situation.
	Thus Melville’s romances do not give the reader
(35)	a full understanding of the complete feelings and
	thoughts that motivate actions and events that shape
	fate. Rather, the romances leave unexplained the
	sequence of events and either simplify or obscure
	motives. Again, such simplifications and obscurities
(40)	exist in order to give prominence to the depiction of
	sharply delineated moral values, values derived from
	a character’s purely personal sense of honor, rather
	than, as in a Jamesian novel, from the conventions of
	society.

    Recently biologists have been interested in a tide-associated periodic behavior displayed by the diatom Hantzschia virgata, a microscopic golden-brown alga that inhabits that portion of a shoreline washed by tides (the intertidal zone).Diatoms of this species, sometimes called "commuter" diatoms, remain burrowed in the sand during high tide, and emerge on the sand surface during the daytime low tide. Just before the sand is inundated by the rising tide, the diatoms burrow again. Some scientists hypothesize that commuter diatoms know that it is low tide because they sense an environmental change, such as an alteration in temperature or a change in pressure caused by tidal movement. However, when diatoms are observed under constant conditions in a laboratory, they still display periodic behavior, continuing to burrow on schedule for several weeks. This indicates that commuter diatoms, rather than relying on environmental cues to keep time, possess an internal pacemaker or biological clock that enables them to anticipate periodic changes in the environment. A commuter diatom has an unusually accurate biological clock, a consequence of the unrelenting environmental pressures to which it is subjected; any diatoms that do not burrow before the tide arrives are washed away.

    This is not to suggest that the period of this biological clock is immutably fixed. Biologists have concluded that even though a diatom does not rely on the environment to keep time, environmental factors—including changes in the tide's hydrostatic pressure, salinity, mechanical agitation, and temperature—can alter the period of its biological clock according to changes in the tidal cycle. In short, the relation between an organism's biological clock and its environment is similar to that between a wristwatch and its owner: the owner cannot make the watch run faster or slower, but can reset the hands. However, this relation is complicated in intertidal dwellers such as commuter diatoms by the fact that these organisms areexposed to the solar-day cycle as well as to the tidal cycle, and sometimes display both solar-day and tidal periods in a single behavior. Commuter diatoms, for example, emerge only during those low tides that occur during the day.