322 RECORD OF CURRENT RESEARCHES RELATING TO 



histological characters are cxhihitcd in sjionges which have been 

 preserved in spirits without any previous treatment. Mr. Norman's 

 specimens are j^erfect as spirit specimens ; they were not preserved 

 with a view to submitting them to detailed histological exami- 

 nation. And here it may be worth while suggesting that if in the 

 future it should be desired to preserve sponges with tliis object, a 

 preliminary soaking in osmic acid solution of • 02 or • 03 per cent, 

 should be given to them before placing them in spirits ; this will 

 effect nearly everything that may be desired. With osmic-acid- 

 treated specimens and the helj) of a freezing microtome, no difficulty 

 should be experienced in obtaining an almost comijlete knowledge of 

 the minute structure of any sponge." 



Collection of Fresh-water Rhizopods — See ante, p. 290. 



Cleaning Diatoms, Seaweeds, &e.*— Mr. G. C. Morris describes 

 a plan which he thinks is more easy than that of M. Petit,t to 

 clean diatomaceous earths (not containing a large percentage of lime), 

 seaweeds, and the ordinary collections from ponds, &c. Dry them in 

 any convenient way and then mix them in a platinum crucible with 

 rather more than an equal bulk of pure bisulphate of potash, and 

 fuse for five minutes at a bright red heat over a Bunsen burner. 

 Such materials as the Jutland cement-stein and guano, which contain 

 a large quantity of lime, must first be soaked in muriatic acid in a 

 test-tube until all action ceases, washed, and then fused in the bi- 

 sulphate of potash. In all cases, after fusing in the bisulphate of 

 potash, allow the mass to cool in the crucible and then place crucible 

 and all in a beaker of water which will dissolve the bisulphate and 

 leave the diatoms and other siliceous matter free from alumina and 

 organic matters. Wash with clean water until there is no acid reac- 

 tion with litmus paper, and then separate the diatoms from the sand 

 as usually directed. 



The advantages of this plan are freedom from the injurious fumes 

 of boiling nitro-muriatic acid, and also from the liability to spurt the 

 acid out of the test-tubes. The diatoms are clean and white, requir- 

 ing no bleaching with chlorate of potash, and the work is all done 

 with one operation, except when the materials contain lime. Even 

 from guano the silica will all come oiit white and clean. With 

 diatoms in situ on seaweed the author sometimes burns the material 

 before adding the bisulj)hate. 



Separating Micro-organisms.+ — In order to reduce the quantity of 

 water containing micro-organisms, obtained by means of a collecting 

 bottle or otherwise, Mr. M. A. Veeder allows the liquid to stand in a 

 bowl until it has settled, and then takes u^) the water by means of a 

 sponge placed in a jpoucli made of fine silk. If the water is allowed to 

 soak into the sponge very gradually, and a slight squeeze is given 

 before removing it from the bowl so as to wash away adherent par- 

 ticles, even the finer organisms diffused through a pint of water may 



* ' Am. M. Micr. Jouni.,' i. (ISSO) p. 38. , 

 t See this Journal, ii. (1879) p. CIG. 

 X ' Am. Nat.,' xiv. (1880) p. 227. 



