The Life-History of Hypotrichoiis Infusoria. 587 



tions as far as possible for hypotrichous Infusoria. With this in 

 mind, experiments on five cultures of hypotrichous Ciliata, includ- 

 ing Oxytricha fallax, Pleurotricha lanceolata, and Gastrostyla 

 steinii, have been carried on during the last three years. Antici- 

 pating the conclusions, it may be stated briefly that the experiments 

 offer aflfirmative evidence upon the first two points and negative 

 evidence upon the last, w^hile owing to failure of the infusorians 

 to conjugate there is no evidence upon the third point. Regarding 

 the fourth and fifth points, it may be said that morphological 

 changes, particularly such as concern the cytoplasmic and macro- 

 nuclear structures, are characteristic of declining vitality, and that 

 initial and daily stimuli have a marked effect upon the metabolic 

 activities of the forms studied. 



I take pleasure in acknowledging my great indebtedness to 

 Professor Gary N. Calkins, at whose suggestion this investigation 

 was undertaken, for his advice and criticism throughout its 

 prosecution. I also wish to express my thanks to Professor 

 Edmund B. Wilson for many helpful suggestions. 



II. GENERAL METHODS AND TECHNIQUE. 



In the experiments on Protozoa here described, which have been 

 followed continuously for the past three years, I have employed, 

 with but slight change, the method used by Calkins ('02, i) which 

 is itself an improvement on the method of Maupas. As this 

 method is described in detail by Calkins, a brief outline of it with 

 my own modifications will suffice. 



The organisms were cultivated on slides having a central cir- 

 cular concavity with a capacity of about five drops of water. 

 Cover-glasses, used by Maupas and Calkins, were not employed, 

 as it seemed to me that a more natural condition was obtained 

 without them, and as I found that unless great care was exercised in 

 cleaning the slips they afforded a possible source of contamination. 

 The slides were kept in moist chambers to prevent evaporation of 

 the preparations. These were ordinary stender dishes about ten 

 inches in diameter and three inches deep. In the bottom of the 

 dish was placed about two inches of wet sand. Over the sand 

 was placed a glass plate on which rested four parallel strips of 

 glass and on these the depression slides with the Protozoa were 

 arranged. The whole was covered with a ground-glass top. 



