1078 SUMMARY OF CURRENT RESEARCHES RELATING TO 



an ordinary metal spoon, and most important of all, a Thorn's 

 " Algen-suchcr " pocket Microscope, which has a magnifying power of 

 150-180 times, with the necessary glass plates and some linen rags 

 for cleaning them. Parchment-paper and guttapercha will also bo 

 found useful for packing up things. It is scarcely necessary to say 

 that owing to the habitat of diatoms waders may be needful. 



Collection should be made, if possible, on a summer day. Water 

 plants, stones, and any other substances seen lying in water, especially 

 in early spring, are to be carefully scrutinized for a brownish- 

 coloured coating. If the Microscope reveal their yellow cell con- 

 tents, the brownish layer may be romoved with the finger to the col- 

 lecting bottle. When the diatoms are found as a soft brownish or 

 blackish scum on the water bottom, this is scooped up with the net, 

 and after draining, is removed with the spoon to the collecting 

 bottle. 



The coarser impurities are removed from the material thus col- 

 lected by straining through a hair sieve into flat ve sels, so as to pro- 

 duce a layer of 1^ to 2 cm. This is set aside in a cool, shady place 

 and covered over with about 1 cm. of water. In one or two days the 

 surface of the muddy layer will be found covered with living diatoms, 

 while the dead and certain varieties unaffected by light, remain 

 buried in the mud. This characteristic may be taken advantage of to 

 procure a pure cultivation of diatoms by merely placing the vessel in 

 the sunshino, when in a short time the diatoms struggle to the sur- 

 face, forming a delicate scum, which is easily removed for examination 

 or for preservation in alcohol. If the residue is required for further 

 cultivation it is supplied with fresh water, and then placed aside in a 

 cool and shady place. Those forms which do not rise to the surface, 

 but are disseminated throughout the mud, are to be obtained for 

 examination by boiling the residue with clean water and decanting off 

 the fluid. 



Another method, which gives better results, but which requires 

 more time, is, after the sifting and the development of the diatoms, to 

 decant off the water, and then keep the mud surface moist by spraying. 

 In four to six days the mud layer has become so consistent that the 

 diatoms may easily be stripped off the surface with a brush. Certain 

 species adhering to water plants, stones, &c, are obtained by sifting 

 from larger impurities, and allowing the water to settle, only brushing 

 the diatoms off. These are preserved either with the objects on 

 which they are found, or the whole collection may be boiled with 

 dilute nitric or hydrochloric acid, and then filtered off to be preserved 

 in the usual way. 



For the cultivation of diatoms it is only required to place the mud 

 collections in flattish vessels in a cool airy place, sheltered from the 

 sun, and covered with a thin layer of water. A constant change of 

 water, the stream of which must not be too strong lest the diatoms be 

 washed away, and kept at a level of 1 cm. high, is extremely useful 

 to the cultivations, which, with care and attention, will last for an in- 

 definite period. About every 14 days it is necessary to stir up the mud 

 layer thoroughly, in order to bring the diatoms into contact with 



