1010 SUMMARY OF CURRENT RESEARCHES RELATING TO 



examined without tlie prism the phosphorescent colonies seem greenish, or 

 even greenish blue. 



Transmitted light is absorbed by the colonies, although absorption- 

 bands are to be perceived. Examined with Zeiss objective A, microspectro- 

 photometer, comparing prism, two Engelmann incandescent lamps, three 

 large Groves, both spectra with a slit of s = s^ = 20 (wherefore 1 = 0*01) 

 were approximately equal, and gradations of light were found which on 

 interposing the colony required for given wave-lengths the following 

 decrease in the slit of the comparing prism : — 



X = 0-66, 0-63, 0-60, 0-57, 0-54, 0-51, 0-48, 0-45. 

 si = 12-1, 12-4, 12-0, 10-8, 9-9, 9-4, 7*7, 6-3. 



By multiplying the numbers found for Sj by 5, the per cent, equivalent of 

 the absorption is obtained. 



These micro-organisms moreover show a vital phenomenon in which 

 they differ from other phosphorescent bacteria. Pure cultivations in 

 salinated gelatin, bouillon, potato, &c., emit light equally well at tempera- 

 tures from 0°-20° C, but cease to give off light at from 32°. So far 

 these properties agree approximately with the results of Pfliiger, but if 

 these bacilli be kept at 35°-37° C. for some hours, their vitality is so im- 

 paired that inoculation from colonies thus treated can no longer be repro- 

 duced in a nutritive medium previously found quite suitable. Yet they 

 will grow almost equally well in a refrigerator, and even if the test-tube be 

 surrounded by finely-powdered ice and then placed in the refrigerator, that 

 is to say, at a temperature of 0° 0. 



MICKOSCOPY. 



o. Instruments. Accessories, &c.* 



(1) Stands. 



Schulze's Aquarium Microscope. — Prof. E. Schulze has designed and 

 Messrs. Klonne and Miiller have made the Microscope shown in fig. 235, 

 for the observation of small aquatic organisms in an aquarium specially 

 constructed for the purpose. There are three parts,— (1) the stand, 

 the greater part of which is nickel-plated; (2) the aquarium; (3) the 

 illuminating mirror. 



The stand consists essentially of a Microscope-tube which is supported 

 in a horizontal position upon a tripod in such a way that it can be moved 

 in three different directions by rack-and-pinion. The column of the 

 tripod carries a rack-and-pinion by which the tube is moved vertically. 

 On the tube which carries the rack is a sliding-piece with a second rack for 

 the horizontal movement from right to left ; upon this slide the Microscope 

 is fixed in a horizontal position and can be moved backwards and forwards 

 in a tube provided with rack-and-pinion. There are therefore three move- 

 ments, vertical, horizontal-lateral, and horizontal-sagittal, so that the 

 organism observed can be followed by the tube as it moves upon the glass 

 wall of the aquarium. 



* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; (3) Illumi- 

 nating and other Apparatus ; (4) Photo-micrography ; (5) Microscopical Optics and 

 Manipulation ; (6) Miscellaneous. 



