INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 847 



of Sorby gradually fades on the addition of hydrochloric acid and 



turpentine The writer has no doubt (taking his stand almost 



entirely upon the charts in M. Petit's jiaper) that the so-called 

 phycoxantliine, in the condition in which M. Petit examines it, con- 

 sists of the yellow xauthophyll of Sorby, with a slight admixture of 

 chlorofucine, true fucoxanthine, and lichnoxanthine, with contamina- 

 tion by imperfect separation of the chlorophyll, which is itself com- 

 pound, and a very little of true phycoxanthine. But whilst we are 

 compelled to regret that M. Petit's work is incomplete, we express 

 our thanks to him for having opened up a new field of inquiry for 

 our diatom friends." 



MICKOSCOPY, &c. 



Microscopical Analysis of Water.* — M. Certes observes that 

 recourse must bo had to the Microscope in order to discover the nature 

 of the minute organisms of water, whether badly infested by them or 

 not. The great difficulty of discovering these bodies in pure waters is 

 best overcome by the use of osmic acid, which also at once kills and 

 preserves them. 



An experiment which shows the efficacy of his method is to place 

 30 c.c. of distilled water in each of two tubes, and in one of them to 

 agitate a glass tube which has been dijjped in water infested with 

 microscopic organisms; to the contents of both tubes equal amounts 

 of osmic acid are added. In examining the water with the Microscope 

 while the one sample shows nothing organized, in the one into which 

 the rod was dipped even the few dead Infusoria are to be found. 



In a drinking water, containing but little organic matter, a solution 

 of osmic acid of the strength of 1 • 5 per 100 is used, and 1 c.c. of this 

 is added to 30 or 40 c.c. of the water ; after some minutes as much 

 more distilled water is added as the vessel will contain (in order to 

 check the action of the acid). The length of time after this at which 

 tlie mixture may be examined varies from a few hours in the case of a 

 highly imj)uro liquid to from twenty-four to twenty-eight for a very 

 pure one; at the cud of the time it must be decanted with great caro, 

 80 as to leave the precipitate in from 1 to 2 c.c. of liquid. 



The use of staining materials has some advantages ; among the best 

 of these materials, M. Certes considers are Ranvier's picrocarmiuo, 

 methyl green, eosiu, haimatoxylin. Paris violet has the recommenda- 

 tion of deeply staining minute and transparent objects ; it should bo 

 very dilute ; it then colours cellulose blue, amyloid matters red, and 

 gives a bluish-violet tint to cilia, flagella, and the protoplasm of 

 Infusoria. Whatever staining matter is used, it is advisable to mix 

 some dilute glycerine with it previously to use, care being taken not 

 to allow the organisms to be shrivelled by too rapid action of tho 

 glycerine of the mixture ; they arc thus kept transparent, and may 

 bo preserved well in tlie glycerine. 



♦ ' Coinptca RenduH,' xc. (18S0) p. 1 135. 



