STUDIES IN THE LIFE-HISTORY OF EUGLENA. 327 



light areas which appear as vacuoles, of varying number and 

 distribution, can be observed at all times during the cycle. No 

 centriole has been observed within the mass. 



The Chromatophores. 



The presence of chromatophores is characteristic of all but two 

 species of Euglena heretofore described. They occur in varying 

 numbers in the different species and are usually described as being 

 of characteristic shape for each species. In E. agilis they appear 

 differently at different stages in the cycle. In the resting stages 

 they are rod shape, arranged parallel to the long axis of the body, 

 and with a distinct pyrenoid in the center. During the stages 

 preparatory to division as well as during the reconstruction of the 

 daughter cells after division, they appear to be more rounded or 

 oblong, much larger and with the pyrenoid quite indistinct or 

 apparently absent. The number likewise is variable, since they 

 are apparently distributed to the daughter animals in some cases 

 before the cell divides and in other cases they divide before cell 

 division and thus give a larger count in the body. These facts 

 lead one to believe that this feature of the cell of Euglena is not a 

 satisfactory basis for the classification of the group. A few 

 preliminary observations on the effect of varying H-ion concen- 

 tration in the culture medium indicates that the form, number 

 and arrangement of the chromatophores is affected by changes in 

 the culture medium. More work needs to be done on this point. 



The Motor Apparatus. 



This consists of a single flagellum and related structures as 

 described below. It extends through the gullet, usually lying on 

 the side nearest the stigma or eye-spot, and ends at one side of 

 the lower border of the reservoir in two distinct branches, each 

 terminated by a granule. The two branches are unequal in size 

 and structure and perhaps also in function. The branch nearest 

 the side of the gullet and reservoir is larger than the other and has 

 a lens shaped enlargement at the point where the gullet widens 

 into the reservoir, apparently underneath the stigma. This 

 arrangement is similar to that described by Wager for E. viridis. 

 The continuation of this branch appears to form the external 



