566 



RESPIRATORY EXCHANGE IN AQUATIC ORGANISMS 



placed on a slide in a few drops of liquid from a Bodo culture. A 

 cover-glass, supported at its four corners by wax feet, is placed over 

 the liquid and is pressed down so that the larva is just prevented 

 from moving, without being injured by the pressure (Fig. 1). The 

 flagellates in the neighborhood of the larva swim in to its surface, 



b 



Fig. 2. 



Fig. 1. 



Fig. 1. Chironomus larva which has just been placed in a suspension of flagel- 

 lates, a, ventral gills; h, anal gills. In all diagrams the density of the dots 

 represents the density of distribution of the flageUates. 



Fig. 2. The same larva shortly afterwards. The flageUates collect on the sur- 

 faces of the larva which are absorbing oxygen. 



