any incipient disposition to other pursuits, they encourage his mathematical bias with a perfect psychological skill.  His brain grows, or at least the mathematical faculties of his brain grow, and the rest of him only so much as is necessary to sustain this essential part of him.  At last, save for rest and food, his one delight lies in the exercise and display of his faculty, his one interest in its application, his sole society with other specialists in his own line.  His brain grows continually larger, at least so far as the portions engaging in mathematics are concerned; they bulge ever larger and seem to suck all life and vigour from the rest of his frame.  His limbs shrivel, his heart and digestive organs diminish, his insect face is hidden under its bulging contours.  His voice becomes a mere stridulation for the stating of formula; he seems deaf to all but properly enunciated problems.  The faculty of laughter, save for the sudden discovery of some paradox, is lost to him; his deepest emotion is the evolution of a novel computation.  And so he attains his end.

“Or, again, a Selenite appointed to be a minder of mooncalves is from his earliest years induced to think and live mooncalf, to find his pleasure in mooncalf lore, his exercise in their tending and pursuit.  He is trained to become wiry and active, his eye is indurated to the tight wrappings, the angular contours that constitute a ‘smart mooncalfishness.’  He takes at last no interest in the deeper part of the moon; he regards all Selenites not equally versed in mooncalves with indifference, derision, or hostility.  His thoughts are of mooncalf pastures, and his dialect an accomplished mooncalf technique.  So also he loves his work, and discharges in perfect happiness the duty that justifies his being.  And so it is with all sorts and conditions of Selenites—­each is a perfect unit in a world machine....

“These beings with big heads, on whom the intellectual labours fall, form a sort of aristocracy in this strange society, and at the head of them, quintessential of the moon, is that marvellous gigantic ganglion the Grand Lunar, into whose presence I am finally to come.  The unlimited development of the minds of the intellectual class is rendered possible by the absence of any bony skull in the lunar anatomy, that strange box of bone that clamps about the developing brain of man, imperiously insisting ’thus far and no farther’ to all his possibilities.  They fall into three main classes differing greatly in influence and respect.  There are administrators, of whom Phi-oo is one, Selenites of considerable initiative and versatility, responsible each for a certain cubic content of the moon’s bulk; the experts like the football-headed thinker, who are trained to perform certain special operations; and the erudite, who are the repositories of all knowledge.  To the latter class belongs Tsi-puff, the first lunar professor of terrestrial languages.  With regard to these latter, it is a curious little thing to note