410 



KNOWLEDGE. 



OCTOBICK. 1911. 



and rod bearing the pivot insures the safety of the moving 

 coil system against a great deal of rough usage. 



THE LL'MI.NOSITV OF THE ElKEFLV.^Coblentz and 

 Ives have made an investigation of the light emitted by the 

 firefly (Photiiiiis pyralis). They find that the radiation con- 

 trolled by the By is all in the visible region of the spectrum — 

 there appears to be very little ultra-violet radiation and no 

 infra-red. The light is under control of the insect and does 

 not appear to be stimulated by pre\ious exposure to light, as 

 with true phosphorescent substances. It is more probable 

 that the light is due to oxidation of some complicated unstable 

 fatty substance, the decomposition of which can be accelerated 

 at will by the insect, perhaps by a catalytic agent. 



M.\(iNETIC ALLOYS.— .^n alloy of 62-0 per cent, of 

 copper, 25-0 per cent, of manganese, and 12-5 per cent, of 

 aluminium, and also another alloy 43-4 per cent, of copper, 

 18-1 per cent, of manganese, and 40-0 per cent, of tin 

 are the two most strongly magnetic of the non-ferrous 

 alloys. Ross and Gray have recently studied the effect 

 of annealing and quenching of these alloys and of such 

 simpler and less magnetic alloys as copper manganese, 

 manganese antimony, and manganese bisnuith. They find 

 that cooling to a very low temperature increases their suscepti- 

 bility. Annealing improves their stability and quenching 

 reduces the hysteresis (or lag of induced magnetism after the 

 magnetising force). It appears to be difficult to explain why 

 such alloys should be magnetic, though in most cases the 

 magnetic properties seem to be due to the formation of solid 

 solutions of binary systems (such as Mn.; .AL) in the rest of the 

 material. 



ZOOLOGY. 



By Professor J. Arihl'R Thomson. M..^. 



MAGNALIA NATURAE: OK. THE, CKl^ATEK 

 PROBLEMS OF BIOLOGY.— This was the title of the 

 notable address which Professor D'Arcy Wentworth 

 Thompson, C.B., gave as President of the Zoological Section 

 of the British Association. F"rom its earliest beginnings, he 

 said. Biology has been a great and complex and many-sided 

 thing. Aristotle was all that we mean by naturalist and 

 biologist ; he gathered up and wove into his great web the 

 varied lore of fishermen and bee-keeping peasants, as well as 

 the learning of the Hippocratic and other schools of physicians 

 and anatomists ; but " every here and there, in words that are 

 unmistakably the master's own, we hear him speak of what 

 are still the great problems and even the hidden mysteries of 

 our science," the magnalia naturae, inquiry into which is 

 characteristic of the spirit of our time. The old questions 

 of vital activity and organic form, of growth and reproduction, 

 of heredity and variation, and the like, are being re-discussed, 

 and many sciences are now being brought to the aid of 

 biology. Very noteworthy is the renewed interest in the 

 validity of the rival interpretations offered by the mechanistic 

 and the vitalistic schools, whose antithetic views recall those 

 of Democritus and Aristotle respectively. But whether we 

 lean to the one side or the other, we must agree in the use of 

 physical methods, and Professor Thompson devoted a con- 

 siderable part of his address to showing that these are of 

 service in studying form as well as function. Surface-tension, 

 for instance, must count for much in determining form ; it is 

 one of the " means of morphogenesis," to use Driesch's 

 phrase. After • giving interesting examples. Professor 

 Thompson expressed his belief that " the forces of surface- 

 tension, elasticity and pressure are adequate to account for a 

 great nuiltitude of the simpler phenomena, and the permuta- 

 tions and combinations thereof, that are illustrated in organic 

 form." . . . But " though we push such explanations to 

 the uttermost, and learn much in so doing, they will not touch 

 the heart of the great problems that lie deeper than the 

 physical plane. Over the ultimate problems and causes of 

 vitality, over what is implied in the organization of the living 

 organism, we shall be left wondering still." 



MOMENTUM IX EVOLUTION.— Professor Arthur Oendy 

 made an interesting suggestion at the British Association in 

 regard to cases where animals or parts of animals seem to 

 have acquired some sort of momentum, by virtue of which 

 they grow far beyond the limit of utility. Is there any con- 

 stitutional brake on growth, and, if so, are there occasions on 

 which the brake may be removed with results which ultimately 

 prove fatal r Professor Dendy asks us to consider the internal 

 secretions or " hormones " which in some cases act as a 

 check on over-growth. If it were advantageous for a structure 

 to grow big. and if that structure were one which grew 

 abnormally big when a particular internal secretion was 

 absent, then natural selection would favour those individuals 

 in which the relevant glands were least developed or least 

 efficient. The glands might disappear, or might cease to pro- 

 duce the particular hormone in question. The organ would 

 go on growing larger ; it would in the course of time reach its 

 optimum : but the brake having been removed, further growth 

 would proceed irrespective of utility. And as to exaggerated 

 structures which never had any value as adaptations. Pro- 

 fessor Dendy appeals to correlation. The removal of a gland 

 which controlled the development of a frontal horn might be 

 followed by the exuberant growth of an entirely useless 

 excrescenci'. 



ARISTOTLE'S LANTERN AS AN OKoAN OF 

 LOCOMOTION. — Dr. James F". Gemmill connnunicated 

 to the British Association a most interesting study of this 

 wonderful piece of mechanism which Aristotle saw over two 

 thousand years ago. There is a rhythmic swinging movement 

 of the lantern, and progression is by a series of steps or 

 lurches which are more or less sharply defined. In each step 

 the urchin is raised on the tips of the teeth and a forward 

 impulse is given. Ui) by strong pushing or poling on the part 

 of the lantern. l6) by similar but usually less effective pushing 

 on the part of the spines, and (cl, after a certain stage, by the 

 influence of gra\'ity. The lantern is then retracted and the 

 teeth swing forward into position for initiating a new lurch. 

 For ordinary locomotion over more or less horizontal surfaces 

 under water the lantern is not needed, but Dr. (iemmill 

 indicated various conditions, normal and experimental, in 

 which it may be employed with effect. " The locomotor 

 action of the lantern is a particular manifestation of a 

 rhythmic functional activity, which can also subserve feeding, 

 boring, respiration, and possibly also the maintenance of 

 physiological turgescence in various internal cavities." 



FOOD SUPl'LY OF AOUATIC ANIMALS.— Dr. W. 

 J. Dakin brought forward at the British Association some 

 interesting corroborations of Putter's theory that sea or fresh 

 water is more or less a nutrient fluid, there being more organic 

 carbon present in solution in the water than there is in the 

 multitudinous plankton that swarms there. Dr. Dakin has 

 tried to estimate the amount of carbon and oxygen required by 

 certain aquatic animals per day to cover the loss due to 

 metabolism. On the basis of this estimate, which is probably 

 verv approximate, a sponge 60 grammes in weight would require 

 to filter several thousand times its own volume of water per hour 

 in order to obtain sufficient food — " an altogether unthinkable 

 piece of work." A big Jelly fish iRhizostoiiia) would require 

 over seven millions of nauplius larvae per day. " It is quite 

 impossible for such large cjuantities to be caught, and eiiually 

 strange that remains of the creatures are so rarely found if 

 they have been captured as food." Another striking fact, or 

 result of calculations at all events, is that the "producers" 

 (the plant-planktont. are insufiicient for the "consumers" 

 (the animal plankton). High alpine lakes, for instance, in 

 which there is an outstanding production of animal plankton, 

 are almost deserts as far as plant-plankton is concerned. 

 What do these alpine crustaceans and rotifers feed on ? 

 Putter's theory is the only solution of the riddle. We come 

 to the idea that the water in lake and sea is food as well as 

 drink. There is bread in the waters — according to the 

 ingenious showing of Dr. D.ikiii. 



