ADAPTATION IN NATURE 359 



ordinary workers (sterile females of the first type), soldiers (sterile 

 females of the second type), and sometimes officers (especially large 

 and powerful sterile females that seem to direct the line of march in 

 legionary ants). All of these casts are produced from the eggs of 

 female and are the result of various special diets permitted the larvae 

 by the workers. Among bees, similarly, there is one queen, a number 

 of drones (males), and the sterile female workers, who perform the 

 functions of nursing the larvae, cleaning up the hive, collecting pollen 

 and nectar, and making honey and wax. Detailed accounts of the 

 lives of bees have been given by various authors, notably by Maeter- 

 linck in his Life 0} the Bee. 



ADAPTATIONS OF DEEr-SEA ANIMALS AND OF 

 CAVE ANIMALS 



One of the weirdest environments the world affords is the bottom 

 of the sea at great depths. There it is dark and cold and almost devoid 

 of oxygen, while the pressure is almost unbelievably high. Yet in these 

 vast and forbidding abysses there dwell in apparent comfort represen- 

 tatives of most of the animal phyla. Fishes of many sorts, crabs, 

 mollusks, worms, and many other forms thrive and multiply in this 

 seemingly cheerless environment. We do not at all understand the 

 nature of the adaptive mechanism that enables these animals to with- 

 stand with their frail bodies the steel-crushing pressures that prevail 

 at all such depths. We do know, however, how some of the deficien- 

 cies of the environment are made good by these denizens of the deep. 

 Thus many abysmal forms produce their own light by means of 

 phosphorescent organs placed at advantageous points of their bodies. 

 Not only fishes of the depths, but some mollusks possess forms of 

 artificial lighting equipment. One species of cephalopod (related to 

 the octopus) is described by Wiesmann as bordered with twenty large 

 phosphorescent lanterns that present the aspect of a display of varie- 

 gated gems, colored ultramarine, ruby red, sky blue, and silvery white. 



Equally highly adapted to life in a world of darkness, the monotony 

 of which is broken only by the occasional spots of light emanating 

 from the various living lanterns just referred to, are the strange eyes 

 of some of the abysmal fishes. Sometimes these eyes are enormously 

 large, and thus adapted to bring to the perception of the animal the 

 weak light of the depths, or again they may be modified still further 

 in a strikingly peculiar manner, each being drawn out into a cylinder 

 and projecting from the side of the head like a telescope. Such eyes 

 are in fact not telescopes, though they are called "telescope eyes," but 

 are merely adaptations for concentrating the lights of low intensity 



