THE BEGINNINGS OF LIFE. 



403 



4. The supervention of less favourable conditions 

 during the progress of the last-mentioned change will 



Fig. 79. 



Lower Transformations of the substance of Nitella. ( X 600.) 



a, a'. Amceboid masses of different sizes, densely packed with bright- 

 green chlorophyll corpuscles. 

 h. A similar mass after decolourization — constituting an ' em- 

 bryonal sphere.' 

 c. An embryonal sphere segmenting into Monads (c'), but leaving 

 a dark-coloured refuse-heap. 

 d, e,f. Three interchangeable developments of smaller embryonal 

 spheres : d, a sporangium giving birth to an arborescent 

 outgrowth; e, a sporangium which subsequently segments 

 into Monads ; /, a large kind of Pythium which subsequently 

 develops its usual blind tube (/'). 

 g, g', g". Three forms of Sporangia which are occasionally formed from 

 the central portions of embryonal spheres. 



put a stop to it, and cause change No. i to proceed. 

 In this case, whilst the peripheral portions of the 

 embryonal sphere are metamorphosed into Monads, the 



D d 2 



