Parsimony 

 Past 



SCIENTIFIC SIDE-LIGHTS 



510 



gun or bow or the weight of his stone; the 

 pianist of the visible position of the note on 

 the keyboard; the singer of his throat or 

 breathing; the balancer of his feet on the 

 rope, or his hand or chin under the pole. 

 But little by little they succeeded in drop- 

 ping all this supernumerary consciousness, 

 and they became secure in their movements 

 exactly in proportion as they did so. 

 JAMES Psychology, vol. ii, ch. 26, p. 496. 

 (H. H. & Co., 1899.) 



2509. PARTHENOGENESIS, NATURE 

 FURNISHES INSTANCES OF Successive 

 Generations of a Single Sex. One of the 

 most remarkable deviations from the normal 

 law of development is seen in the case of the 

 little aphides, or plant-lice, the insects so 

 familiar to all as the pests of the gardener. 

 At the close of the autumn season winged 

 males and females of these insects appear 

 amongst their neighbor-aphides, and these 

 produce eggs, which, however, lie dormant 

 throughout the winter. Waking into life 

 and development with the returning spring, 

 these eggs give birth each to a wingless fe- 

 male, no insect of the sterner sex being 

 found amongst the developed progeny of 

 these insects. The presence of both sexes 

 is throughout the animal world regarded as 

 necessary for the production of eggs capable 

 of developing into offspring. Strangely 

 enough, however, these wingless females not 

 only produce eggs, hatching them within 

 their bodies, but the eggs develop into beings 

 exactly resembling themselves, not a single 

 male aphis being represented within the lim- 

 its of this amazonian population. Seven, 

 eight, nine, or even eleven generations of 

 these wingless females may be produced in 

 this manner, and the swarms of plant-lice 

 which infest our vegetation attest the fer- 

 tility of the race. But in the last brood 

 of these insects, produced toward the close 

 of autumn, winged males appear in addition 

 to the females, which latter also possess 

 wings. The members of this last brood 

 produce eggs of ordinary nature, which lie 

 dormant during the winter, but which in 

 the succeeding spring will inaugurate the 

 same strange life history through which 

 their progenitors passed. . . . The law 

 of heredity appears to operate in this in- 

 stance in a somewhat abnormal, or at any 

 rate in a very unusual manner. The true 

 similitude of the winged parents is not at- 

 tained until after the lapse of months, and 

 through the interference, as it were, of many 

 generations of dissimilar individuals. AN- 

 DREW WILSON The Law of Likeness, p. 37. 

 (Hum., 1888.) 



20 1O. PARTICLES SMALLER THAN 

 LIGHT-WAVES Microscope Does Not Reveal 

 Them. Our best microscopes can readily 

 reveal objects not more than B0 fl 00 of an 

 inch in diameter. This is less than the 

 length of a wave of red light. Indeed, a 

 first-rate microscope would enable us to 

 discern objects not exceeding in diameter 



the length of the smallest waves of the visi- 

 ble spectrum. By the microscope, therefore, 

 we can test our particles. If they be as 

 large as the light-waves they will infallibly 

 be seen; and if they be not so seen, it is 

 because they are smaller. Some months ago 

 I placed in the hands of our president a 

 liquid containing Briicke's precipitate [of 

 resin from alcoholic solution let fall in 

 water]. The liquid was milky blue, and 

 Mr. Huxley applied to it his highest micro- 

 scopic power. He satisfied me tRat had 



particles of even yWtnnj- of an inch in di ~ 

 ameter existed in the liquid they could not 

 have escaped detection. But no particles 

 were seen. Under the microscope the tur- 

 bid liquid was not to be distinguished from 

 distilled water. TYNDALL Fragments of Sci- 

 ence, vol. ii, ch. 8, p. 119. (A., 1897.) 



2511. PARTICLES, SUPPOSED, OF 

 LIGHT Newton's "Emission Theory" Mis- 

 taken Analogy of Gravitation. Newton's 

 conceptions regarding the nature of light 

 were influenced by his previous knowledge. 

 He had been pondering over the phenomena 

 of gravitation, and had made himself at 

 home amid the operations of this universal 

 power. Perhaps his mind at this time was 

 too freshly and too deeply imbued with 

 these notions to permit of his forming an 

 unfettered judgment regarding the nature 

 of light. Be that as it may, Newton saw in 

 refraction the action of an attractive force 

 exerted on the light-particles. He carried 

 his conception out with the most severe 

 consistency. Dropping vertically downwards 

 towards the earth's surface, the motion of a 

 body is accelerated as it approaches the 

 earth. Dropping in the same manner down- 

 wards on a horizontal surface, say through 

 air on glass or water, the velocity of the 

 light-particles, when they came close to the 

 surface, was, according to Newton, also ac- 

 celerated. Approaching such a surface 

 obliquely, he supposed the particles, when 

 close to it, to be drawn down upon it, as a 

 projectile is drawn by gravity to the surface 

 of the earth. This deflection was, accord- 

 ing to Newton, . . . refraction. . . . 

 Finally, it was supposed that differences of 

 color might be due to differences in the size 

 of the particles. This was the physical 

 theory of light enunciated and defended by 

 Newton; and you will observe that it 

 simply consists in the transference of con- 

 ceptions born in the world of the senses to 

 a subsensible world. TYNDALL Lectures on 

 Light, lect. 2, p. 46. (A., 1898.) 



2512. PARTICLES, VIEWLESS, OF 

 ODOR Rotary Motion of Odorous Substances. 

 Since the interesting discovery of Romieu, 

 in 1756, that very small bits of camphor on 

 the surface of water have a curious rotary 

 motion, the same phenomenon has been 

 noticed by a number of observers in several 

 hundred odorous substances of either vege- 

 table or animal structure. This, of course, 

 strengthens the belief that the stimulus of 



