xiv Introduction 



an abundance of fine specimens by placing small pieces 

 of bark from trees or pond sides in small aquaria. , After 

 the culture vessel has stood in a warm room two or three 

 weeks, remove the piece of bark from the water, and with 

 a fine brush scrape off on to a glass slide some of the 

 liquid adhering to it. Frequently there will be dozens of 

 amoebse in a single mount. By floating a cover glass on 

 the surface of the water of a jar containing amoebse and 

 kept in a diffuse light for a day or two, specimens may 

 be obtained free from sediment. 



In studying the amceba, one should not be content with 

 small amoeboid creatures having no contractile vacuole. 

 The large typical specimens showing contractile vacuole 

 and the nucleus may be obtained by a series of such 

 aquarium cultures as are here described. If the aquarium 

 is in a north window, it is well to put it in a warm sunny 

 situation a few hours before studying, as the amoebae thus 

 become much more active, and are of greater value for study. 

 With such specimens the vacuole may be seen to contract, 

 the distinction between the endosarc and the ectosarc may 

 be made but, the ingestion and egestion of food particles 

 may be observed, and my latest classes in zoology saw the 

 whole process of reproduction by fission. 



The nucleus may be brought out in the amoeba by 

 staining with iodine, methyl green, or blue, and with various 

 other reagents. 



If the water in a culture jar in which amoebae are abun- 

 dant is allowed slowly to evaporate, one will often be 

 able to get good examples to illustrate the process of 

 encystment. If the jar is finally allowed to become dry 

 and is then stored away, the culture may be started again 

 months later by adding water — a method first suggested, 

 I believe, by Professor Herbert Osborn. 



