OF HETEROGENBSIS 213 



the usual light-green, fatty-looking corpuscles. In B another of 

 these bodies is shown which was crowded with motionless, resting 

 Amcebas, the largest one, below, possessing a distinct nucleus. 

 They were decolourised, but mixed up within the cyst with refuse 

 granular pigment. 



In C another smaller resting spore is seen full of much more 

 rudimentary spherical masses, whose substance was distinctly and 

 coarsely granular, rather than composed of clear protoplasm as in 

 the nucleated specimen above referred to. These specimens were 

 found in the midst of a mixture of Vaucheria and Spirogyra 

 filaments, and the smaller one was kept under a cover-glass for 

 three days in the hope that development of the organisms might 

 proceed, distilled water being added day by day. It is rare, 

 however, for these changes to proceed much under such unfavour- 

 able conditions. The photograph D was taken at the end of 

 this period. The spore was somewhat pressed out of shape by the 

 daily subtraction and addition of water, preceding and following 

 examination with the microscope, but the Amoeba had become 

 more distinct, rather less granular, and two or three of them showed 

 the appearance of a nucleus. 



(f) Transformation of the Substance of Euglenae into 



Amoebae. 



The production of Amoebae from the substance of Euglenas is a 

 change that takes place with great frequency, both in small and 

 in large specimens, when they are in an encysted condition. In 

 the former case only one to three Amoebae may be produced, but 

 in large specimens as many as ten or twelve may be produced 

 within a single Euglena. After their production the Amoebas 

 remain as motionless spheres, it may be for two or three weeks, 

 gradually increasing in size, while the original Euglena cyst slowly 

 disintegrates or softens, and disappears. 



If a portion of a Euglena pellicle is kept for a week or ten days 

 in the dark, this kind of transformation is very commonly to be 

 seen in some of them. 



The photographs which I have selected for illustrating this 

 process were taken from some large Euglenae obtained about the 

 middle of September, 1900, from the border of a small lake at 

 Loughton, where they formed a pale but bright green coherent 

 film. After they had been kept indoors in a dim Ught for ten days 



