INTRODUCTION. 13 



is shallow enough, a large test-tube is very convenient,, 

 the mouth being stopped by the thumb until the 

 bottom is reached, or a bottle will answer the same 

 IDurpose ; to collect from water-plants or algae thes& 

 should be gently squeezed into a wide-mouthed bottle, 

 and after allowing a short interval for settlement, the 

 upper portion may be poured away and the bottle 

 replenished, the process being repeated several times. 

 For preservation for future examination the sediment 

 thus collected can be put into small tubes or bottled 

 (^-oz. or 1-oz. size) and about 5 per cent, of carbolic 

 acid or formaline added — or alcohol (spirits-of-wine) 

 may be substituted for the water. If methylated 

 spirit is used it must be of the kind that does not 

 become cloudy on the addition of water. To collect 

 plankton material a net of fine silk or calico can be 

 towed from a boat, care being taken that the net is 

 deep enough to prevent the contents from escaping ; 

 a galvanised iron ring about 10 inches in diameter 

 is a convenient size on which to make the net. The 

 gatherings may be kept in glass jars or in bowls out 

 of the direct sunlight. 



It is best to locate a specimen on the slide under 

 the microscope previous to putting on a cover-glass, 

 isolate it in a drop of clean water, and then place 

 a cover-glass oyer it; the plasma, pseudopodia, etc., 

 should be examined as far as it is possible to do so in 

 the living state, and a careful drawing made, after 

 which, if the endoplasm is hidden by the various 

 inclusions, the water under the cover-glass may be 

 allowed to evaporate until the envelope is ruptured 

 and the contents are forced out. 



To examine the component parts of the envelope 

 the specimen should be immersed in dilute sulphuric 

 acid by which means the chitinous and silicious 

 elements are isolated; strong sulphuric acid will 

 dissolve chitin and leave only the silicious parts. 



