892 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Stokes, G. G. — On Light as a means of Investigation. Burnett Lectures. 

 Second Course. 114 pp., 8vo, London, 1885. 



The " Times " on the Microscope. \_Supra, p. 883.] 



Times, 1885, August 26th. Cf. also February 16th. 

 Veerall, G. H. — Micro-photography for illustrating the neuration of trans- 

 parent winged insects. 



[Note of successful experiments.] Proc. Entomol. Soc. Lond., 1885, p. iv, 



"Walmsley's (W. H.) Photo-micrograph of Rinnbach's arranged Diatoms. 

 [Cf. ante, p. 530.] 



The Microscope, V. (1885) p. 181. 

 Ward, K. H.— The Binocular. [Posf] 



Micr. Bulletin (Queen's), IL (1885) pp. 28-9 (1 fig.) 

 from The Microscope in Botany (Behrens). 



i9. Collecting, Mounting and Examining Objects, &c. 



Method for Observing Protoplasmic Continuity.* — M. L. Olivier 

 recalls that three years ago he pointed out that photography applied 

 to the study of minute objects revealed details of structure which 

 made no impression on the retina, and that in support of this he 

 instanced a photograph which showed on the walls of the cells 

 markings and perforations invisible under the Microscope. He now 

 further illustrates the matter by reference to the canals which 

 traverse the cell-walls of plants. 



The existence of these canals escapes the ordinary processes of 

 investigation, but can be shown by the employment of photography. 



Thin transverse sections are made of living tissues whose growth 

 is complete. A direct photograph is taken of the sections, with an 

 amplification of 300 to 700. On these negatives, examined with a 

 lens, the cell-membranes seem to be in a very surprising state of com- 

 plication : perforated in various ways, with canals, some transverse, 

 others longitudinal, that establish a communication between the 

 contents of the cells. It seems impossible to explain by a pheno- 

 menon of diffraction this appearance of canals on the photographic 

 plates. 



After having made out this structure on the negatives, the author 

 endeavoured to see them by direct vision and examined the prepara- 

 tions under an amplification of 700-900, in a dark chamber into 

 which the Microscope was introduced, in such a way that the eye 

 received no other impression than that of the light coming from the 

 instrument. Under these conditions he succeeded in distinctly seeing 

 the interruptions of the cell- walls in many plants. 



Direct observation is, however, in most cases quite insufficient, 

 and the author obtained a better result by staining, either the cell- 

 membranes of his preparations, or the protoplasmic elements after 

 fixing, turgescence or contraction by means of appropriate reagents. 

 In the first case the septa presented here and there colourless lacunte, 

 at least in certain species of plants. In the second case the walls 

 of the cells were white against the coloured ground; the canals 

 which traverse the septa are then visible, since they are coloured like 



* Comptes Rendus, c. (1885) pp. 1168-71. 



