256 



THE BIOLOGY OF HYDRA : 1961 



^^' 





-1^'- 



Fig. 1. Electron micrograph of a transverse section through a musculo- 

 epitheiial cell of an anemone showing the intracellular location of an algal 

 cell, a) animal cell, b) algal cell, c) chromatophore. d) pyrenoid. (Prepared 

 with the assistance of Miss Jane Westfall) 



at Pacific Grove, California, served as controls and are referred to 

 as albinos. 



In order to evaluate quantitatively the effect of the algae on 

 the nutrition of the host, we measured changes in weight of normal 

 and albino anemones starved in light and darkness for 11 weeks. 

 Reduced weight, i.e., weight under water, was used to measure 

 weight changes. This method eliminates error from surplus fluid 

 and, in contrast to dry weight, allows repeated measurements on 

 living individuals.^ 



^There were no major changes in the specific gravity of the animals themselves 

 during the course of the experiment, showing that all of the observed changes were 

 true weight changes. 



