tom. It was, when complete, a marvel of disguise. Whether because of its rarity or the effectiveness of its concealment, I have never found another.

No one needs instruction regarding the effect of such artificial aids to inconspicuousness on bottoms they cover by acres. A laboratory specimen would tell the tale almost as effectively as one in the open.

SCORPAENA WEARS TATTERS FOR A DISGUISE

Among fishes, those that haunt by preference a particular type of bottom sometimes reveal the nature of their dwelling place as clearly as the disguised snail.

Scorpæna, with its tatters of dermal filaments hanging about its lips and from the spines and ridges of its large and rugged head, or from fin spines and sides of the body, is a miracle of disguising coloration, as it lies still upon an algacovered bottom, making no move for hours, except the inconspicuous opening and closing of its opercular cleft to control the water stream bathing its gills.

I saw one a day or two ago and had fairly to rub its back before I could con

vince myself that it was not actually overgrown by the film of algae its color imitated. Even in a cement tank the meaning of its decoration would be clear.

One might imagine the hours of quiet it spends, unbroken, as I have seen, even when a hermit crab drags its shell across the fish's outspread fins. Imagine, as I have seen, also, the impetuous, engulfing rush with which at last it seizes unwary small fishes that have, perhaps, accepted it as a part of its surroundings.

THE LITTLE TUNNY STOWS ITS FINS IN

GROOVES

Not less obviously shaped and colored adaptively is the little tunny (Gymnosarda alleterata), not greatly different, except in size, from the tuna, well known to all devotees of rod and reel. Its shapely body is in every line designed for speed, and no detail is omitted that tends to preserve the perfection of its streamlines.

The high dorsal fin folds smoothly down in a deep groove in the back, a device common enough. But, most unusually, pectorals and ventrals at rest

also fit perfectly into depressions in the smooth surface countersunk to receive them. The hand might be passed back over them without the sense of touch discovering them, so precise is the workmanship.

In the matter of color, similar perfection in detail is manifest. When the pectoral fin is fully extended it stands horizontally out at right angles to the body.

The ventrals similarly extended are spread in the same horizontal plane, and the upper surfaces of all are dark like the back; but the lower surface of the extended pectoral is glistening silver, and that of the ventral fin pure lusterless white.

As a result, when they are appressed to the body they not only sink into the depressions waiting to receive them, but the one pair is lost in the metallic silver of the side and the other in the flat white of the belly, with which they agree precisely in their respective positions.

By contrast, had I not had the good fortune to see them using their odd equipment, I should never have known why a large mantis shrimp at Tortugas has the last joint of its walking legs studded with bristles until they look like bottle brushes, or why the little crab Petrolisthes has on each joint of its last limbs, serving as jaws, a great tuft of fringed hairs.

I flexed and extended the maxillipeds of Petrolisthes, spread out the hair tufts. that readily opened; yet the essence of their function escaped me before, in a fissure facing the tide, I saw the creatures throw these organs wide to form a great hemispherical funnel that caught drifting microscopic material until inturned,

cleaned, and held forth again for Nature's bounty.

And I venture to say regarding the shrimp that no mere anatomical study, however thorough, would ever induce in the mind's eye a clear image of the animal standing in its burrow in incoherent sand, with its several pairs of flattened palms, its crooked elbows, and ten bushy feet bearing against the walls and keeping them from collapsing.

FIELD STUDY ALONE CAN SOLVE MANY RIDDLES

Here the difficulty in conceiving the service rendered by elaborate structures is due solely to that in visualizing the conditions under which they function, though these themselves, when discovered, may prove rather simple.

But where the element of compromise, to which I have referred earlier (see text, page 81), enters as it frequently does in the realm of coloration, field study-and then more field study-is absolutely necessary before the often marvelously effective disguises may be apprehended in their true relations.

On a ground color that matches one background against which it is commonly seen, bars appear, matching another entirely different. Contrastive patterns in gay colors result, which seem impossible to explain as useful; but to the enlightened eye these, no less than the more obviously serviceable structures described, illustrate that adaptation to environment which characterizes not only animals of the coral reefs, but which from the time of Aristotle has been recognized as a distinctive feature of living things.

99

THE WORLD AS DEPICTED BY MAP-MAKERS BEFORE CAPTAIN COOK'S FIRST VOYAGE TO "THE GREAT SOUTH SEA' This chart. reproduced from Moll's Atlas, published in London about the time of Cook's first voyage, emphasizes especially how little was then known of the west coast of North America, a region which Cook explored on his third voyage (see, also, map, page 87).

Ο

NE can picture him coming up to Whitby a tall, angular lad, his cheeks ruddy after his crosscountry tramp in the sea air from Staithes. What would he do first-inflamed with this crazy idea of going to sea, so crazy that, failing to explain it satisfactorily to his employer, he ran away-what would he do, but go to the docks and mingle with the sailors?

What a town and what sights for a boy who had felt the call of the sea! Down a narrow street, evil-smelling, the landsman would say, between red-roofed, close-built houses, past ship chandlers with nets and blocks and tackle and sails, he trudged to the water front. There, riding at anchor, were the whalers and colliers and merchantmen; this one bound for Bremen with iron and stone; that one for Danzig, or maybe even St. Petersburg, with jet or alum; a third, the one with the stern sails, just in from Penzance.

The fishermen are lolling about, pipes in mouths, indolent and slouching, until midnight galvanizes them into action. Thereafter the raging storms of the German Ocean and its icy breath alternately bedevil and benumb them.

A HABERDASHER'S CLERK YEARNS FOR
A SAILOR'S LIFE

The boy, wide-eyed, open-mouthed, pack still on shoulder, was a target for this loutish crew. "Name, son?"

"James Cook, sir."

Then perhaps a hesitating inquiry about a berth on some ship, and counterquestions about age, experience, his people; why he wanted to sign up for such a dog's life, anyway.

NEW-WORLD DISCOVERY CULMINATES
WITH COOK

Every boy yearns to see the world; but it is likely that no other boy has grown up to fulfill that yearning so completely as Captain James Cook, R. N., the circumnavigator.

School children study the conquests of Alexander and Napoleon, but they come upon surprisingly little about the bloodless, enduring victories of Magellan, Marco Polo, Vasco da Gama, and Cook. One widely discussed list of men who influenced the course of world history sent readers scurrying to reference books to identify Asoka, but omitted mention of Columbus.

If only for the strange, unheard-of things he saw-people who played flutes with their nostrils, curious birds of amazing colors, canoes as big as the vessel he commanded, savages who roasted dogs in crude fireless cookers, calendars that went by the moon, an animal that a sailor at first took for the devil (it was the first kangaroo seen by a white man)—these and other queer, new spectacles make Cook's voyages fascinating as narratives.