6o8 Lorande Loss Woodruff. 



The general behavior of individuals on the slide is quite different 

 at various periods in the life-cycle, and by it the condition of the 

 culture can be estimated with some degree of accuracy. Although 

 the activity of the animals is considerably lessened during depres- 

 sion periods, I have not found that their power of taking food is 

 diminished since the oral cilia vibrate normally and keep a con- 

 tinuous stream of food particles passing into the mouth opening, 

 and this results in a black appearance of .the infusorians due to 

 accumulated and unassimilated food. 



Another indication of physiological disturbances during periods 

 of depression is the greater frequency of pathological divisions at 

 this time, and Calkins found this to be the case in Paramoecium 

 cultures. An interesting specimen which occurred in the A-cul- 

 ture of Oxytricha, when the vitality was extremely low in June, 

 1902, is shown in Fig. 21. 



2. Morphological Variation. 



For the purpose of determining the morphological changes 

 which occur during the life-history, permanent preparations were 

 made from time to time during the life of each of the cultures.^ 

 The series of preparations is particularly complete for the Oxy- 

 tricha A-culture, from the time that series was approaching its 

 first depression period through its recovery by stimulation, and 

 then through the second cycle which resulted in death. On this 

 account, the following description is based on this series of some 

 two hundred slides, while the lesser series of Oxytricha B, Pleuro- 

 tricha A, and B, and Gastrostyla A are used for confirmation and 

 comparison. 



The typical cytoplasmic structure of Oxytricha fallax, Pleuro- 

 tricha lanceolata, and Gastrostyla steinii, is practically identical 

 and is best described as alveolar throughout. As in all the hypo- 

 trichida, no distinction is visible between ectoplasm and endo- 

 plasm. The ectoplasmic modifications such as cilia, cirri, and 

 membranelles, of course, vary in a characteristic manner for each 

 species, but it is unnecessary to consider these here. In Oxy- 

 tricha and Pleurotricha, as is well known, there are two ellipsoidal 

 macronuclei situated more or less symmetrically in the cell, while 



*For description of technique, see section on General Methods and Technique. 



