NOTES AND MEMOEANDA. 151 



The modus operandi seems to be that the steam penetrates the 

 pores of the wood or other substances, and forces out the air, whose 

 place it takes. The air is then absorbed by or dissolved in the sur- 

 rounding medium. The woody fibres are not destroyed by the hot 

 and compressed steam, except the soft tissues, as one would at first 

 sight suppose. They are entirely uninjured, and their purposes for 

 microscopic study remain as good as by any other process. Tender 

 specimens in every case must be tenderly treated. This mode of 

 procedure has been followed by several microscopists in America for 

 two or three years, and all the specimens so treated have been remarked 

 for their beauty and excellence. 



Immersion Illuminators. — Mr. Wenham thinks that too much is 

 said in favour of the prism which he described in 1856 * (intended to 

 be attached to the under surface of the slide by oil of cloves), by some 

 who take it up as a recent discovery. He at once abandoned it in 

 favour of a lens nearly hemispherical, of about ^^ radius, which is 

 much more convenient and effective for all purposes, and less costly. 

 This lens is then attached to the under side of the slide by the oil, in 

 the same way as the prism, or it may be set in a thin plate of brass to 

 be slid under the slide and centred under a low power if necessary ; 

 or otherwise mounted in a sub-stage fitting of such a form as not to 

 interfere with the passage of the most oblique rays that can be sent 

 into it sideways, which are by this appliance transmitted straight to 

 the object. When used with a dry objective, the object is seen on a 

 dark field, the rays being reflected from the top of the cover, which 

 acts as a Lieberkuhn.| 



In a letter to ourselves Mr. Wenham says that he finds no illu- 

 minator equals it, for he can immediately bring out Ampliipleura 

 without the least trouble, even when mounted in balsam ; a feat that 

 has sometimes before cost him half an hour's work. 



Phosphorescence of the Flesh of Lobsters. — The following view 

 of the cause of this phosphorescence is put forward by Messrs. Bancel 

 and Husson.J The first alteration observed in the flesh of marine 

 animals is the formation of a gelatinous substance, and it is then 

 that phosphorescence appears. 



Examined under the Microscope, two kinds of germs are seen ; on 

 the surface, cells which without doubt produce this kind of mucous 

 fermentation ; in the mucus, infinitely small bacteria. 



The former, which are of a reddish yellow, are aerobic, and 

 appear to act as plants, that is, that during the day they decompose 

 the carbonic acid of the air, fixing the carbon and setting the oxygen 

 free, which remains in solution in the liquid. 



If this liquid contains an anaerobic germ, its development is arrested 

 — it is anaesthetized. But in the night the cell disengages carbonic 

 acid, the germ lives, and the consequences are the destruction of the 



* ' Quart. Joum. Mic. Sci.,' vol. ii. (1856) p. 2; and see this Journal, vol. i. 

 (1878) p. 309. 



t 'English Mechanic,' vol. xxviii. (1879) p. 501. 

 X ' Comptes Kendus,' vol. Ixxxviii. (1879) p. 191. 



