122 



THE POPULAR SCIENCE MONTHLY. 



tion, by taking deep and slow inspirations 

 say twelve or fifteen a minute. By this 

 means the action of the heart will become 

 slower and feebler, less blood is thrown into 

 the brain, and very soon a quiet feeling, 

 ending in sleep, is induced. As by a slight 

 effort of the will any one may try this, we 

 leave the question of its value to the test 

 of actual experiment. 



A New Optif.il Experiment. Mr. Wil- 

 liam Terrill offers in Nature a new lecture- 

 experiment for proving the compound na- 

 ture of white light. This method is to ar- 

 range seven lanterns so as to project their 

 several circles of light side by side on a 

 white screen, then to color each circle by 

 introducing slides of glass stained to imi- 

 tate the seven colors of the spectrum (the 

 proper intensity of color being found by 

 trial); in this way are produced seven cir- 

 cles on the screen, colored from red to vio- 

 let, and arranged side by side. Then by 

 turning the several lanterns, so that the pro- 

 jected circles exactly overlap each other, 

 one circle of white light is obtained, prov- 

 ing that the seven colors together make 

 white light. The same effect can be pro- 

 duced with five colors only, if properly se- 

 lected ; and even two, the ordinary cobalt- 

 blue and deep orange, will nearly do. If 

 these two be made to partially overlap, the 

 effect is very striking. 



Dalliuger's Stndies of Minute Animal 

 Forms. The Rev. W. H. Dallinger, whose 

 researches into the origin and development 

 of minute life-forms have earned for him a 

 distinguished plnce in the world of science, 

 in a communication to the Royal Institution 

 of Great Britain, gives a brief historical 

 sketch of his labors in this field. Ten 

 years ago Mr. Dallinger determined to work 

 out, by actual microscopic observation, the 

 life-history of some of the lowly and minute 

 organisms which occur in putrid infusions. 

 After four years of preparation, he com- 

 menced his wink in conjunction with Dr. 

 Drysdale, the plan needing two observers. 

 Each set of observations was made con- 

 tinuous, so that nothing should have to 

 be inferred. Very high powers were em- 

 ployed, and the largest adult objects ex- 

 amined were tbW of an inch, the smallest 



40W Six forms altogether were selected, 

 and their whole history was worked out. 

 At first it was supposed that reproduction 

 by fission was the usual method, but pro- 

 longed research showed that spores were 

 produced. These were so small that a 

 magnifying power of 5,000 diameters was 

 needed to see them as they began to grow. 

 The glairy fluid from which they developed 

 seemed at first homogeneous, and it was 

 only when growth set in that the spores 

 became visible. All that could be learned 

 about the origin of the glairy fluid was, that 

 a monad larger than usual, and with a gran- 

 ulated aspect toward the flagellate end, 

 would seize on one in the ordinary condi- 

 tion ; the two would swim about together till 

 the larger absorbed the smaller, and the two 

 were fused together. A motionless spheroid- 

 al glossy speck was then all that could be 

 seen. This speck was found to be a sac, 

 and, after remaining still from ten to thirty- 

 six hours, it burst, and the glairy fluid 

 flowed out. The young spores that came 

 into view in this were watched through to 

 the adult condition. Bearing on the sub- 

 ject of spontaneous generation, this fact 

 was learned, that, while a temperature of 

 140 Fahr. was sufficient to cause the death 

 of adults, the spores were able to grow even 

 after having been heated to 800 Fahr. for 

 ten minutes. That there is no such thing 

 as spontaneous generation of monads seems 

 to Mr. Dallinger quite clear; and he is sat- 

 isfied that, when bacteria are studied after 

 the same manner, the same law will be 

 found to hold good with them. 



Influence of the Environment. As a 



striking instance of the transformation ef- 

 fected in a race by changed conditions of 

 life, Das Ausland quotes, from Khanikoff 's 

 "Memoir on the Ethnography of Persia," 

 some observations on a colony of Wiirtem- 

 bergers which in 1816 settled in the trans- 

 Caucasus country, near Tiflis. The original 

 colonists, we are informed, were "singularly 

 ugly," with broad, square countenances, 

 blond or red hair, and blue eyes. The sec- 

 ond generation showed some improvement ; 

 black hair and black eyes were no longer 

 rare. The third generation was so entirely 

 altered that their Wiirtemberg descent was 

 no longer visible, for now black hair and 



