Purpose 

 Qualifications 



SCIENTIFIC SIDE-LIGHTS 



568 



gradually, in accordance with certain laws, 

 so that we are often able to watch every stage 

 of the transition from the full development 

 of an organ to the entire absence of it. 

 WEISMANN Heredity, vol. ii, ch. 9, p. 6. 

 (Cl. P., 1891.) 



28O2. The Key to Struc- 

 ture How Darwin " Neglected This Plain 

 Guide." The idea of special use, as the con- 

 trolling principle of construction, is so im- 

 pressed on Mr. Darwin's mind that in every 

 detail of structure, however singular or ob- 

 scure, he has absolute faith that in this lies 

 the ultimate explanation. If an organ is 

 largely developed, it is because some special 

 purpose is to be fulfilled. If it is aborted 

 or rudimentary, it is because that purpose 

 is no longer to be subserved. In the case 

 of another species whose structure is very 

 singular Mr. Darwin had great difficulty 

 in discovering how the mechanism was meant 

 to work so as to effect the purpose. At last 

 lie made it out, and of the clue which led 

 to the discovery he says : " The strange 

 position of the labellum perched on the 

 summit of the column ought to have shown 

 me that here was the place for experiment. 

 I ought to have scorned the notion that the 

 labellum w r as thus placed for no good pur- 

 pose. I neglected this plain guide, and for 

 a long time completely failed to understand 

 the flower." [" Fertilization of Orchids," p. 

 262.] ARGYLL Reign of Law, ch. 1, p. 23. 

 (Burt.) 



2803. PURPOSE, MANIFESTED BY 

 MONKEY I observed to-day that if a nut 

 or any object he [a capuchin monkey] 

 wishes to get hold of is beyond the reach 

 of his chain he puts out a stick to draw 

 it towards him, or, if that does not suc- 

 ceed, he stands upright and throws a shawl 

 back over his head, holding it by the two 

 corners so that it falls down his back; he 

 then throws it forward with all his strength, 

 still holding on by the corners; thus it goes 

 out far in front of him and covers the nut, 

 which he then draws towards him by pulling 

 in the shawl. When his chain becomes 

 twisted round the bars of a " clothes-horse " 



(which is given him to run about upon), 

 and thus too short for his comfort, he looks 

 at it intently and pulls it with his fingers 

 this way and that, and when he sees how the 

 turns are taken he deliberately goes round 

 and round the bars, first this way, then 

 that, until the chain is quite disentangled. 

 ROMANES Animal Intelligence (extract from 

 diary of author's sister), ch. 17, p. 486. (A., 



1899.) 



2804. PURPOSE MISUNDERSTOOD 



Bird Not Buoyed Up by Air-cells Why the 

 Bird's Bones Are Hollow. The common ex- 

 planation of birds being assisted by air- 

 cells for the inhalation and storage of heated 

 air must not only be erroneous, but founded 

 on wholly false conceptions of the funda- 

 mental mechanical principles on which flight 

 depends. If a bird could inhale enough 



warm air to make it buoyant, its power 

 of flight would be effectually destroyed. 

 It would become as light as a balloon, and 

 consequently as helpless. If, on the other 

 hand, it were merely to inflate itself with 

 a small quantity of hot air insufficient to 

 produce buoyancy, but sufficient to increase 

 its bulk, the only effect would be to expose 

 it to increased resistance in cleaving the 

 air. It is true, indeed, that the bones of 

 birds are made more hollow and lighter 

 than the bones of mammals, because birds, 

 tho requiring weight, must not have too 

 much of it. It is true, also, that the air 

 must have access to these hollows, else they 

 would be unable to resist atmospheric pres- 

 sure. But it is no part whatever of the 

 plan or intention of the structure of birds, 

 or of any part of that structure, to afford 

 balloon-space for heated air with a view to 

 buoyancy. ARGYLL Reign of Law, ch. 3, p. 

 87. (Burt.) 



2805. PURPOSE OF CIRCULATION 

 ON THE SUN The Reverse of That on the 

 Earth. The solar system of circulation, in- 

 stead of being adapted, like that of the 

 earth, to the distribution of heat received 

 from without, was seen to be directed to- 

 wards the transportation towards the sur- 

 face of the heat contained within. Polar 

 and equatorial currents, tending to a purely 

 superficial equalization of temperature, were 

 replaced by vertical currents bringing up 

 successive portions of the intensely heated 

 interior mass, to contribute their share in 

 turn to the radiation into space which might 

 be called the proper function of a sun. 

 CLERKE History of Astronomy, pt. ii, ch. 2, 

 p. 187. (Bl., 1893.) 



2806. PURPOSE, SELECTIVE, OF 



HONEY-BEE Plan Changed to Meet Difficul- 

 ties. Finally, in places where special con- 

 ditions of the situation do not otherwise 

 permit, it may be observed that the bees, 

 far from clinging obstinately to their plan, 

 very well understand how to accommodate 

 themselves to circumstances not only in cell- 

 building, but also in making their combs. 

 F. Huber tried to mislead their instinct, 

 or rather to put to the proof their reason 

 and cleverness in every possible way, but 

 they always emerged triumphant from the 

 ordeal. For instance, he put bees in a hive the 

 floor and roof of which were made of glass, 

 that is, of a body which the bees use very 

 unwillingly for the attachment of their 

 combs on account of its smoothness. Thus 

 the possibility of building as usual from 

 above downwards, and also from below up- 

 wards, was taken away from them; they 

 had no point of support save the perpendicu- 

 lar walls of their dwelling. They thereupon 

 built on one of these walls a regular stratum 

 of cells, from which, building sideways, they 

 tried to carry the comb to the opposite side 

 of the hive. To prevent this, Huber covered 

 that side also with glass. But what way 

 out of the difficulty was found by the clever 



