MICROSCOPIC OBJECTS. 



161 



(10.) Method of selecting Aquatic Larva, and other small 

 Animals. — The animals described in several of the pre- 

 ceding chapters* are large and visible to the eye. These 

 require to be kept in vessels of considerable dimensions, 

 which renders it difficult to select any particular specimen, 

 as is also the case with the more minute ones in phials. 

 For effecting this purpose Ledermuller has described and 

 figured in plate 87 of his work a very ingenious contriv- 

 ance ; it is simply a glass tube open at both ends, and 

 is employed in the following manner :— Hold the tube 

 by the upper end between the fingers, and close the 

 orifice by the thumb (see the annexed figure); then 



immerse the lower end in the vessel of water, and the 

 instant the insect desired approaches the end of the tube, 

 remove the thumb from the upper end, and the pressure 



* See Notes on Natural History. 



