STUDIES ON EUGLENAMORPHA HEGNERI. 163 



been discovered. When one realizes that such a transformation 

 does take place it is almost like having seen evolution occur. 



Zumstein and Ternitz point out that their results do away with 

 the boundary line between the genera Euglena and Astasia which 

 had been separated on the basis of the presence or absence of color 

 (chlorophyll and stigma). The differences between the type of 

 E. hegneri and its variety pcllucia are much more extensive and 

 serve to emphasize the indistinctness, at times, of systematic 

 boundaries. 



There is nothing in the observations made on the green and 

 colorless variety of E. hegneri to indicate that either ingests solid 

 food. Indeed, the writer is extremely doubtful if any of the 

 Euglenidee ever become holozoic. Those bearing chlorophyll must 

 be thought of as largely holophytic in their mode of nutrition, 

 while the colorless ones are probably saprozoic (saprophytic). 



Assuming that the green variety of E. hegneri transforms into 

 the colorless one, it is perhaps surprising that there are so few 

 intermediate stages. Valid transition stages are, in fact, rather 

 rare. If one were inclined to argue against transformation, the 

 following objections to it could be raised: (i) the great extent of 

 morphological differences between the two varieties; (2) the rela- 

 tive stability of the two forms; (3) the rareness of intermediate 

 stages ; (4) the occasional occurrence of large numbers of pel- 

 lucida which may outnumber the type as found on prepared slides ; 

 (5) the absence of direct observation of the transformation. It 

 can further be argued that degeneration of the green variety leads 

 to their death, and that the pellucid variety may have a stage in 

 which there is some chlorophyll. 



Most of these difficulties can, however, be satisfactorily ex- 

 plained. The colorless variety, while fairly distinct, is too un- 

 stable to be a permanent type. This instability is indicated by ( I ) 

 the probably abnormal hypertrophy and amitotic division of the 

 nucleus; (2) the extreme variation in the surface striations ; (3) 

 the variations in the number of flagella ; (4) the probably abnormal 

 enlargement of the reservoir (excretory system) ; (5) its failure, 

 so far as observed, to form a resting stage which could be carried 

 over from one host to another. 



