380 SUMMARY OF CURRENT RESEARCHES RELATING TO 



been proved. M. Dareste recently observed that there were in the 

 albumen of an egg some pellicles of bran perfectly recognizable by 

 their structure, and by the considerable number of starch-grains 

 which they contained j these pellicles were quite 1 mm. in diameter. 

 The diameter of the spores can only be reckoned by thousandths of 

 a millimetre. 



In the experiments above described the eggs were in an atmo- 

 sphere completely saturated with hiimidity in consequence of the 

 insensible transpiration of the egg, but even in the ordinary condi- 

 tions of incubation the spores enclosed within it may germinate, and 

 the greater or less abundance of the vegetation may completely pre- 

 vent the development of the embryo or arrest it after it has begun. 

 This is one of the principal causes of the premature death of the 

 embryo, and also of the inequalities constantly observed in the results 

 of incubation. 



Biology of Bacteria.* — During his researches on bacteria as 

 reagents for the physiological disengagement of oxygen,| T. W. 

 Engelmann had occasion to examine whether light could exercise 

 a direct action on the movements of the bacteria. Nothing had at 

 that time suggested such an influence. Experiments had been made 

 on the ordinary bacteria of putrefaction (B. termo). The temperature, 

 the tension of the oxygen, the proportion of carbonic acid, the con- 

 centration of the medium, the intensity, the colour and duration of 

 action of the light had been modified in very different ways. 



Later on, whilst repeating these same experiments on Vibrios and 

 Spirilla, the author also obtained negative results, with one single 

 exception. 



A drop of water, which, besides a quantity of Spirillum tenue, only 

 contained a few specimens of Micrococcus and a Bacterium of larger 

 size (2-3 jx) being illuminated over a very small portion of its 

 surface, there collected in less than half a minute,| at the illuminated 

 spot, hundreds of Spirilla and, besides, some of the little cocci and 

 larger bacteria. In the dark, and even in green or blue light, they 

 re-distributed themselves, but not in the red light, even where it was 

 of relatively feeble intensity. It may be presumed from this fact 

 that there was a disengagement of oxygen, for when the gas failed 

 them, the organisms in question accumulated round every source of 

 oxygen (air-bubble, edge of the glass, cover-glass, and green cells) 

 which was accessible to them. 



The accumulation of Spirilla and bacteria at the illuminated spot 

 did not take place when the drop of water was uncovered and in 

 continuous contact with the atmospheric air or with a mixture of 

 hydrogen and oxygen. They accumulated, however, as soon as a 

 current of pure hydrogen was passed through the gas-chamber, to 

 disappear again almost immediately as soon as a little oxygen was 

 allowed to enter. 



* Rev. Internat. Sci., ix. (1882) pp. 276-8. See also Bot. Ztg., xl. (1882) 

 pp. 321-5, 337-41. t See this Journal, i. (1881) p. 962. 



X At least when the preparation had remained for some minutes covered with 

 a thin glass. 



