324 WOOLFORD B. BAKER. 



P.M. During that period the divisions stages are the most 

 numerous. Twenty cc. of the material was taken at thirty 

 minute intervals, centrifuged, killed, and either stained en masse 

 or taken from the centrifuge tube, placed on cover glasses and 

 stained according to that method. The first method gives good 

 results when the material is abundant. Material killed at ten 

 P.M. gave the greatest number of stages of mitosis. After 

 twelve P.M. most of the divisions initiated around eight P.M. 

 have been completed, and from twelve P.M. to six A.M. very few 

 dividing forms can be found in the culture. 



The animals in a culture appear to be active during the day but 

 usually about five P.M. they become less active, some assuming a 

 spherical shape then extending the body again and again as if 

 undergoing intense metabolic activity. This difference in the 

 cyclical phases of Euglena agilis as observed at different times of 

 the day, and especially the nocturnal incidence of dividing forms 

 may be explained perhaps by the difference in the carbon dioxide 

 content of the medium at different times. At evening and during 

 the night the photosynthetic processes which have gone on during 

 the day are retarded and cease. The normal activity of the 

 animals would then increase the relative amount of carbon 

 dioxide present and perhaps influence the changes which are 

 observed. Sufficient data have not yet been obtained to prove 

 the validity of such an assumption. 



GENERAL MORPHOLOGY. 



The description of Euglena agilis as given by Carter and quoted 

 from Kent is as follows: 



"Body somewhat flask-shaped, inflated and widest posteriorly, 

 attenuate anteriorly; a short, blunt caudal prolongation some- 

 times present, but not essential; multiplying in the active 

 condition by longitudinal and transverse fission, and in its passive 

 or encysted one by crucial or by linear segmentation ; color green, 

 movements very active. Length 1/600 inch." 



The species used in the present study conforms to this de- 

 scription except for the fact that it does not divide by transverse 

 fission. In addition there are certain characters observed which 

 seem to be diagnostic: 



