Marvels of Pond-Life. 127 



are found attached to sticks, stones, or leaves, generally 

 to the under surface of the latter. They are all objects 

 of great interest and beauty, which, whatever their diver- ' 

 sity, conform sufficiently to one type that the student 

 who has observed one, will easily recognise the zoological 

 position of another. They should be viewed by trans- 

 mitted and by dark-ground illumination, which produces 

 very beautiful effects. To observe them in the perform- 

 ance of their functions, they require more room than 

 the live-box can afford, but are well shown in the glass 

 trough, whose moveable diaphragm enables them to be 

 brought near enough to the object-glass, for the use of 

 a power of about sixty linear for general purposes, and 

 of from one to two hundred for the examination of 

 particular parts. For a more detailed examination 

 dissection must be employed, but all that we have men- 

 tioned can be seen without injury to the living animal, 

 if specimens are kept till new cells are formed in water, 

 which does not contain enough dirt to render their in- 

 teguments opaque. 



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