166 PROCEEDINGS OF THE SOCIETY. 



Mr. W. J. SoUas's letter on the subject of cutting sections of diatoms 

 was formally laid before the meeting. It had reference to the paper 

 of Dr. Flogel, read at the December meeting, and was also intended 

 to be read at that meeting, but did not come to hand until the meeting 

 was over, when it was informally communicated to those present. The 

 letter was as follows : — 



" For some time past I have been engaged in cutting sections of 

 diatoms. My plan is to scrape off a green slime from our river mud, 

 consisting chiefly oi Pleurosigma zigzag — a large species suitable for 

 cutting. The slime, together with some mud, unavoidably gathered 

 at the same time, is placed in a saucer and covered with a piece of 

 muslin, which lies in immediate contact with the mud, while a film of 

 water lies above it. The saucer is now exposed to daylight, and the 

 diatoms creep through the muslin, collecting in a consistent film 

 on its upper surface. The muslin may now be lifted from the mud, 

 it comes away clean bringing all the diatoms with it, but leaving the 

 mud. The muslin with the diatom film is now immersed in the usual 

 hardening and staining reagents. I have used a mixture of chromic 

 and osmic acids and absolute alcohol for hardening ; borax-carmine, 

 haematoxylin, and eosin for staining. "When duly stained and hardened 

 the diatom films may be removed from the muslin without difficulty, 

 and cut, either by imbedding in pure paraffin (melting point 68°) and 

 mounting in Canada balsam, or by freezing in gelatine jelly, which 

 allows one to cut consistent sections wMcli may he mounted direct in 

 glycerine on a glass slide, without passing through water. By em- 

 ploying these two processes, I have made out the internal structure of 

 diatoms, and believe that I can detect fine protoplasmic threads pro- 

 ceeding from the protoplasm that surrounds the nucleus and passing 

 through apertures in the median keel. I am not yet, however, in a 

 postion to demonstrate this with absolute certainty, but hope to do 

 so soon." 



Dr. Beale gave a resume of his paper on " The Constituents of 

 Sewage in the Mud of the Thames " (p. 1), illustrating his remarks by 

 numerous drawings, and pointing out the important bearing of the 

 matter upon the question of the health of the population of London in 

 the probably near future. 



The President thought the Society would feel greatly indebted to 

 Dr. Beale for bringing before it this very unpleasant subject in a truly 

 scientific spirit. Of its great importance from a sanitary point of view 

 there could be no manner of doubt. 



Mr. Bennett said he could confirm from his own experience the 

 view expressed by Dr. Beale, that by no means all of the sewage of 

 London was discharged into the Thames. As an instance in point, 

 he might say that he had lived for some time in the north of London, 

 and had recently discovered that there was no connection between the 

 house and the main drain, but that the house drains merely led to a 

 cesspool. He was told that this was the case with at least half the 

 other houses in the road. He should be sorry to appear to throw the 

 slightest doubt on any point touched upon by Dr. Beale, as of course. 



