86 C. L. HOOD. 



Another feature that seems worthy of further investigation 

 may be observed in the camera lucida drawings given in Fig. I ; 

 e.g., the evident decrease in the size of the host as the zoo- 

 chlorellae disappear. Minchin quotes Popoff as observing these 

 variations in size of Frontonia leucas and crediting them to a 

 difference in temperature of the media in which the Frontonia 

 live. 



The experiments of this paper were conducted in a laboratory 

 where both large and small, infected and uninfected Frontonia 

 were exposed to the same conditions of temperature. Yet 

 differences of as much as 100 microns have been found in speci- 

 mens taken from the same culture, and these variations have 

 persisted throughout the study. Therefore it seems unlikely 

 that temperature could have had any part in this variation. 



Of fifty specimens, without zoochlorellae, measured, the average 

 length was 225 microns, while the nucleus averaged 16 microns 

 in length. Of fifty specimens, with innumerable zoochlorellae, 

 measured, the average length was 310 microns and the nucleus 

 averaged 18 microns in length. 



These observations tend to demonstrate that a mass relation 

 exists between cytoplasm and nucleus. Similar nucleoplasmic 

 relations have been demonstrated in different species of Arcella 

 by Hegner (1920) and Reynolds (1923). 



Lipska (1910) found that when placed in the dark, Paramecium 

 caudatum with zoochlorellse would live eight days or more, 

 that Paramecium without zoochlorellae died between the second 

 and fourth days, and concluded that the zoochlorellae were 

 responsible for the greater resistance shown by the Paramecium 

 with zoochlorellae, in that they furnished a supply of oxygen. 



The following experiment was carried out with Frontonia 

 leucas: Specimens with zoochlorellae were placed in darkness, 

 in their original culture medium, and exposed to the same con- 

 ditions of temperature as before, but no appreciable difference 

 was noticed in their death rate as compared with those in the 

 light. This, however, does not preclude the possibility of the 

 host obtaining oxygen from the zoochlorellae, because in darkness, 

 where photosynthesis is impossible, zoochlorellae cannot give off 

 oxygen. 



