288 CORRESPONDENCE. 



approval I return my best thanks, and join with them in the belief 

 that no unfair criticism or semi-official opposition, although sufficiently 

 annoying at times, will seriously impede our onward progress. 



I remain, Sir, yours faithfully, 



H. Davis. 



The Figures in Mr. Stodder's Paper in the 'Lens.' 



To the Editor of the ' Monthly Microscopical Journal? 



Sir, — Permit me to say to Mr. Slack that I agree with him, that 

 the "figure" all the figures, intended to illustrate my paper in the 

 ' Lens ' on Eupodiscus Argus, is " not quite correct " or nearly so. 

 The fact is, I am no draughtsman, and the sketches were only ex- 

 pected to give an approximate idea of the appearances, and the printed 

 figures give but an approximate idea of the originals. I did not see any 

 proof of the printed figures, or they would have been altered or sup- 

 pressed. The " irregular hexagons " were distinctly irregular, not the 

 effect of distortion — Figs. 4 and 5, perhaps, the best representation of 

 the real appearance of any, but can be seen only by reflected light, 

 and a high power. Fig. 2 is certainly the worst of all, and is unlike 

 anything that I saw — as I did not think, and do not now, that the 

 terms " areola? " and " cellules " are confined to botany, but are words 

 in common use ; I use them as descriptive, without regard to any 

 technical meaning as applied to other plants, if they have any such. 



The real structure and constitution of the silicious shell of the 

 diatoms is a study that will tax the skill, patience, and instruments of 

 the best microscopists. I hope that some of the English workers will 

 devote more time to solving the problems. It is of far more worth 

 than making new species. My ideas of the structure are to be found 

 in the ' Quarterly Journal of Microscopical Science,' vol. iii., N. S., 

 p. 214. 



Following up the investigation since with higher magnifying 

 powers and immersion lenses, I have found but little reason to change 

 my opinions. I do not believe that all diatoms are built up alike ; I do 

 not believe, notwithstanding all that has been written and published on 

 the question, that the structure of the Pleurosigmata is settled. Re- 

 cently I examined one with a Tolles' ^th by sunlight. At one focal 

 adjustment I got hexagons as sharp and distinct as those of Triceratium 

 fat us ; a minute change of focus gave beads of all the prismatic 

 colours. "Which is true ? Can the appearance of spheres be produced 

 by transparent in any other shape ? The answer to this question in- 

 volves much more than the structure of a diatom ; it affects almost all 

 investigations with the microscope. 



Charles Stoddeb. 



