xii Introduction 



must show the different phases of their growth. In those 

 cases where the organisms are sufficiently abundant in the 

 outer world to be available in quantity, it seldom happens 

 that they present the desired phases of their existence at 

 the time when it is necessary to study them. In a large 

 proportion of cases they are not sufficiently abundant out 

 of doors to be readily obtained in the needed quantity. 



Fortunately these difficulties may to a great extent be 

 overcome by indoor culture of the organisms required. 

 For several years I have been experimenting with such 

 cultures, and in the following pages I have summarized 

 such of the results as seem likely to be of assistance to 

 those who use this book. The apparatus required for such 

 cultures is simple and easily obtained. For the aquarium 

 cultures, glass dishes and jars of almost any size and shape 

 may be used. Perhaps no one general form is so cheap 

 and satisfactory as the special aquarium jars recently 

 placed upon the market by the dealers in microscopes and 

 laboratory supplies. These are of convenient size and 

 shape for cultures of many kinds, and a dozen or more of 

 them are of the greatest value to the work of any zoologi- 

 cal laboratory. Glass covers for them should be pur-: 

 chased. But in case these aquarium jars are not at hand, 

 wide-mouthed museum jars or beakers, or even fruit cans 

 and jelly glasses, will serve the purpose very well. 



THE ASICEBA 



Amoebae may be found in the waters of ponds and 

 ditches, but one is more certain to have them when wanted 

 by providing aquarium cultures. Almost any of the 

 small aquaria described in these pages are likely to furnish 

 good amoebae, if one examines the sediment that gathers 

 on the sides or bottom of the vessel. I have often obtained 



