94 COLLECTING ANIMALCULES 



observe that those persons whom I have found the most successful in 

 these matters, always employ the cheapest and simplest con- 

 trivances. 



Por the larger kinds of Infusoria, and especially those Hving upon 

 aquatic plants floating on the surface of the water, a small net is 

 very nseful. I have for many years used one made as follows : 

 Take a piece of common iron wire about 2 J feet long and |th thick, 

 bend one end into a round hoop about three or four inches in 

 diameter, and turn the other end into a small loop for the handle. 

 Take a piece of fine Irish liaen and make it into a bag, either 

 pointed at the end Hke that shown at page 51 of the "Microscopic 

 Jllustrations," or roimded. This bag, when sewed on to the iron 

 hoop, forms the most convenient appliance I have met with, and 

 may be carried about in the coat pocket. Another appUance which 

 I find of great use, is a small white saucer for the purpose of 

 skimming the water. By this means, numerous kinds of Infusoria, 

 which attach themselves to floating plants, may be captm^ed readily, 

 }ind then transferred to a phial. 



Take with you, also, a pocket magnifier, of shallow power. This 

 may be mounted in various ways ; but the one I prefer is a triple 

 one, having the lenses arranged in the same plane ; the convenience 

 of which is, that you will have three different powers always ready 

 for use, without the necessity of moving them ; and that, the mount- 

 ing being flat, it will be very suitable for the waistcoat pocket. 

 Sling this, with a piece of ribbon, about the neck, and there will be 

 jio danger of losing it. The magnifying powers usually selected, are 

 those from flve to fifty diameters (2 inches to ^ an inch focus) ; the 

 first, or largest, serving to distinguish the masses ; the intermediate, 

 to show the general movements, so as to determine pretty nearly 

 whether the water you have collected is worth retaining or not ; and 

 the smallest, or most powerful, for examining the contents with more 

 minuteness. This latter power will not so frequently be called into 

 use abroad aa at home ; because, with a little practice, the middle 

 &nd shallow powers will be found to answer every purpose. 



The grooved sphere (see Treatise on Optical Instruments, 1828,) 

 now called the < Coddington lens,' is, when moimtcd, a very ex- 

 cellent magnifier for these purposes, as in every position the rays 

 traverse the axis ; but by far the best for definition, is an inverted 



