MICROSCOPY. 245 



iced Journal. Enormous numbers of the calycine and spring- 

 ing monads, when entering freely into the spore-emitting 

 and sac condition, were carefully heated at a temperature 

 of 150 Fahr. until quite dry, flaky, extremely friable, and 

 crumbling into dust with the least pressure. Suitable ves- 

 sels, covered, and partially filled with a nutritive fluid, were 

 placed in a chamber, the air of which could be optically test- 

 ed for the presence of motes or germs by transmitting the 

 condensed beam of an oxvhydrogen lime-light. At the end 

 of four days the searching beam still showed the presence of 

 floating motes, though in greatly diminished quantity, and 

 a i'ew of the vessels, which had meanwhile been uncovered, 

 were now examined. In every drop from these the larger 

 or calycine monad was found, but the springing monad was 

 comparatively rare. Two days after, four of the vessels, 

 which had in the meanwhile been opened and exposed to 

 the air with the diminished number of motes, were exam- 

 ined, and proved to be almost destitute of the calycine 

 monad, but the springing monad was much more abundant. 

 The explanation of this is, that the heavier germs of the lar- 

 ger monad had nearly all fallen before the expiration of two 

 days, but those of the smaller were still lingering in the air. 

 To test this still further, an infusion twelve months old, and 

 composed almost entirely of the very minute uniflagellate 

 monad, was carefully dried at 150 Fahr., reduced to fine pow- 

 der, and intimately mixed with that containing the calycine 

 and springing monads, and diffused in a chamber so that the 

 air could be tested as before by the beam of light. When 

 all the larger particles had fallen, nine vessels of the nutri- 

 tive fluid were introduced. Three of these were open ; the 

 rest were covered. At the end of twenty-four hours two 

 more were opened, and the remaining four were uncovered 

 at the end of forty-two hours. The first set, on examination, 

 yielded all the forms in the ratio of their magnitude, the 

 next set was almost entirely destitute of the larger forms, 

 and the last four absolutely so. Each set was exposed five 

 days. Afterwards, when the beam showed the air to be mote- 

 less, four more vessels with the same nutritive fluid were ex- 

 posed for five days, at the end of which time not a trace of 

 a monad could be found in any of them; and Bacteria which 

 had been more or less present in all the other instances were 



