70 



THE AMEEICAN MONTHLY 



[April, 



membranous capsule — cyst — tlius 

 guard for a long time against com- 

 plete drying, or starvation. If more 

 -water is added the cyst bursts and 

 the animal lives as before. In many 

 species, division into 2, 4, or more 

 individuals takes place within the 

 cysts ; some appear to become en- 

 cysted for this j)urpose alone. 



The minute cysts are lifted up 

 and carried along by the winds from 

 the shores and bottoms of dried up 

 ponds, and widely distributed with 

 the dust which is suspended in the 

 air. The occurrence of Infusoria in 

 all suitable liquids which are exposed 

 can be thus explained without the 

 necessity of assuming their spon- 

 taneous origin {generatio cequivoca). 

 For this reason also, when the air 

 is dry more numerous forms appear 

 than during wet weather. 



The ordinary habitat of the Infu- 

 soria is determined by the food 

 upon which they live, which is 

 partly solid and partly liquid. Some 

 kinds live only in fresh-water among 

 AlgaB, upon which they feed, or 

 among which they find other ani- 

 mals which afford them nourish- 

 ment. Others, which live upon 

 foul organic matter, are found only, 

 or at least in greatest abundance, in 

 stinking puddles or infusions. The 

 last are especially important in the 

 household. They remove foul mat- 

 ter in the shortest time, for they 

 consume the organic detritus before 

 its complete decomposition into its 

 elements. 



The Buflfalo Meeting of the Am- 

 erican Society of Microscopists. 



{Concluded.) 



To observe the course of these 

 burning grains to advantage, cause 

 a pistol charged with coarse 

 powder to be fired in the dark 

 at a distance of a few meters and 

 at right-angles to your line of 



vision, and the tiny projectiles -will 

 be seen to describe graceful curves, 

 each one mimicking, within the 

 range of two or three meters, the 

 trajectory of the leaden bullet in a 

 course five hundred times as long. 

 If the shot be fired through glass at 

 a distance of one or two meters, 

 the ball will pass through leaving a 

 hole that will vary somewhat in 

 appearance according to circum- 

 stances, and the burning powder 

 grains will leave, where they strike 

 the glass, pale, grayish stains which 

 look somewhat like grease-spots, 

 or like the fungoid specks where 

 diseased flies have adhered to the 

 glass in autumn. They may be 

 recognized, however, by their 

 grouping around the bullet-hole, by 

 their microscopical appearance, 

 and by chemical analysis, since 

 they do not behave like grease in 

 the presence of suitable tests ; and 

 Mr. Hagan has repeatedly obtained 

 from them the sulphurous reaction 

 of blackening a microscopic quan- 

 tity of a salt of lead. Being caused 

 by the burning powder-grams, they 

 indicate with certainty that the 

 shot was fired near the surface ; 

 and a further hint as to the distance 

 may sometimes be obtained from 

 the degree of lateral or vertical 

 displacement of the whole cluster 

 as measured from the position 

 of the ball-hole, the trajectory 

 of the grains being considerably 

 modified, and that of the ball not 

 perceptibly so at such distances, by 

 gravity, or by a strong lateral wina. 

 Still more interesting and sugges- 

 tive are the appearances when the 

 grains are fired against wood, paint, 

 clothing or the human face; the 

 latter experiment being often tried 

 by small boys who look into the 

 touch-hole of a small cannon on the 

 Fourth of July, to see whether the 

 cannon is going oif or not, and with 

 the familiar result of being so well 



