ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 813 



sive images on the glass of the man or animal in movement are fixed on 

 a circular plate turning on its centre, and they are made to pass one 

 after auotlier behind an opening in a large screen in front of the ob- 

 server. Every time that one of the images reaches the middle of the 

 aperture it is illuminated during the fraction of a second (about 1/10,000) 

 by the discharge of an induction coil through a Geissler tube placed 

 behind the movable disc." The effect is of course the same as that of 

 the zoetrope or " wheel of life." 



M. Errera's idea of applying this process to microscopic objects is 

 thus expressed : — 



" The details and the mechanism of the movements of microscopic 

 b3ings are still very imperfectly known. The cells with vibratile cilia, 

 the infusoria, and the zoospores still present a crowd of problems to be 

 resolved. I can hardly think that photography, which has rendered 

 such great services in analysing the leap of man, the flight of the sea- 

 gull, and the gallop of the horse, could not also be employed with 

 success in the case of fishes, insects, worms, protozoa, algae, or isolated 

 histological elements, I propose, in conjunction with a skilful photo- 

 grapher, to make some experiments in this direction. The aquarium 

 Microscope of Klonne and Miiller, and that of Nachet with several 

 bodies, suitably modified, will probably allow of the instantaneous 

 photography of microscopic movements." 



Photographing Phosphorescent Bacilli by means of their own 

 light.* — Dr. Fischer has taken good photographs from cultivations of three 

 different phosphorescent bacteria. To do this successfully it is necessary 

 that the cultivation should shed an intense light, the dry plates must be very 

 sensitive, and the exposure long (24-36 hours). The best pictures were 

 obtained from B. phospliorescens, the cultivations of which in a dark 

 room at 5^-10^ C. gave out their brightest light. In these photograms 

 not only are the colonies seen distinctly and sharply formed, but the 

 outlines of the test-tubes and other vessels are recognizable, A herring 

 illuminated with B. pliosphorescens took extremely well, the scales 

 showing with perfect distinctness. The head and tail, which were not 

 illuminated, did not appear in the photograph. 



Dr. Eischer then went a step farther, and obtained photographs of 

 external objects, e. g. a watch, by the illumination of these phospho- 

 rescent colonies in a dark room. Not only could the time be read, but 

 the hands and second-hands were distinctly visible. The illuminant 

 bacteria alluded to are those commented on before in this Journal 

 (ante, p. 277) — the "West Indian" and the " endemic" phosphorescent 

 bacilli, and B. phosjjJiorescens. 



Gkay, W. M. — Photo-micrography. 



[Methods used by the author in photomicrography of sections of aijimal tissues.] 



The Microscope, VIII. (1888) pp. 172-5. 



Neuhatjss, E. — Die Entwickelung der Mikrophotographie in den letzten zwei 



Jahren mit besonderer BeriLcksichtignng ihrer Bedeutung fiir die Lehre von den 



Mikroorganismen. (The development of Pliotomicrography in the last two years 



with special reference to its importance for the theory of micro-organisms.) 



Centralbl.f. Bacterial, tt. Parasitenk., IV. (1888) pp. 81-4, 111-6, 283-4 

 [Also reply by M. Stengltin, ibid., pp. 282-3.] 

 Eaftee's (G. W.) Photomicrographs. 



[Commendatory notice of them.] Amer. Mon. Micr. Joum., IX. (1888) p. 113. 



* Centralbl. f. Bakteriol. u. Parasitenk., iv. (It 88) pp. 89-92. 



