THE RELATIONS OF BURSARIA TO FOOD 



I. SELECTION IN FEEDING AND IN EXTRUSION 



E. J. LUND 



Zoological Laboratory of The Johns Hopkins University 



EIGHT FIGURES 



CONTENTS 



Introduction 2 



Action of the structural mechanism for feeding and the selection of food ... 4 



1. Rejection •■ 5 



2. Acceptance -5 



Formation of the vacuole and elimination of residues 7 



Measurement of the amount of food eaten, and method of experimentation . . 8 



Internal relations affecting the feeding process 10 



1. The relation of the physiological state of the organism to the feeding 

 process 10 



2. Changes in the physiological state as shown by using the feeding proc- 

 ess as an index 16 



3. Other causes of individual variation 19 



The external relations of the feeding process 20 



1. Effects of external factors on feeding 20 



a. Concentration of the food supply 20 



b. Effect of mechanical stimulation and mechanical injury on feeding. 21 



c . Temperature 23 



d. HCl and NaOH 24 



e. White light 24 



f . The electric current 26 



Selection of food and the factors concerned 29 



1. Experiments with stained and unstained yolk 30 



a. Saffranin 30 



b. Janus green 34 



c. Hematoxylin 37 



d. Congo red. 39 



e. Sudan III 40 



f. Stale yolk 40 



2. The basis for and the nature of the selection of food in Bursaria 41 



The relation of Bursaria to digestible and non-digestible substances 43 



1. External relations 43 



2. Internal relations 44 



Summary 51 



Literature cited 52 



1 



THE JOURNAL OF EXPERIMENTAL Z05L0QY, VOL. 16, NO. 1 

 JANUARY, 1914 



