12 LORANDE LOSS WOODRUFF 



The first series of measurements, those of areas, were made 

 with an ocular micrometer cross-ruled into squares. The areas 

 of the cells and nuclei were each plotted twice to obviate errors 

 as far as possible. The unit in which the areas are expressed in 

 the tabulations equals 225 square microns. The second series of 

 measurements were made with an ordinary ocular micrometer. 

 The length and breadth of each cell was determined and also 

 the length and breadth of each of the two macronuclei. It was 

 impossible to measure the thickness of either the cell or nucleus, 

 but from a series of observations it was apparent that the average 

 thickness of the cell is very nearly one half that of the width 

 and that the thickness of the macronucleus* is the same as its 

 width.' Therefore these dimensions, which are without doubt 

 substantially accurate and produce a negligible error, were em- 

 ployed for the third dimension. The results are expressed in cubic 

 microns. 



Throughout this study the term 'nucleus' has taken into ac- 

 count the macronuclei only and the micronuclei have been dis- 

 regarded as in the investigations of former workers in this field. 

 This is justifiable from several standpoints. In the first place 

 the area and the volume of the micronuclei is insignificant in 

 comparison with that of the macronuclei, and actual measure- 

 ments fail to reveal variations which would appreciably affect 

 the results. Second, variations in the number of micronuclei 

 which were noted occurred characteristically during periods of 

 marked physiological degeneration when it was impossible to 

 compute the volumes of the parts of the cell (Periods A and D), 

 and when the macronuclear increase was so great that the micro- 

 nuclear variations would not appreciably affect the area determi- 

 nations. Third, it is well estabhshed that the macronucleus 

 comprises the chromatin specialized for the general vegetative 

 cell activities — and so is of paramount interest in the present 

 connection. 



^ It is apparent, of course, that since these hypotrichous forms are consider- 

 ably flattened dorso-ventrally, the mounted specimens present to view either 

 the dorsal or ventral side of the animal. 



