172 AQUATIC MICROSCOPY FOR BEGINNERS. 



needed. When cold, arrange the arms if necessary, 

 add a drop of weak glycerine and water, and cement 

 the cover-glass' with shellac. The Hydras thus pre- 

 pared can be kept indefinitely, and at any time shown 

 to admiring friends. . I have at this wricing a prepara- 

 tion thus made, and in perfect condition although it 

 is ten years old. 



Both the green and the brown species are abundant 

 during the summer among Anacharis and Lemna. 



