468 THE BEGINNINGS OF LIFE. 



a colourless but thick cyst-like envelope (Fig. 86, h). 

 Very many of these bodies seemed to remain stationary 

 when they had attained the size of two" in diameter ; 

 and some of them might be seen whose contents were 

 undergoing various stages of decolourization, whilst in 

 others, lying by their side, all the colouring matter had 

 disappeared and was replaced by a mass of structureless 

 protoplasm containing a few granules of different sizes 

 (_;, k). These masses of protoplasm gradually underwent 

 a series of molecular changes, during which old granules 

 disappeared and new granules, of a rather large size, 

 took their place. The mass then began to shape itself, 

 whilst cilia developed at each extremity, by means of 

 which it commenced rotating irregularly within its cyst, 

 the walls of which had now become much thinner (/). 

 The form of an Oxytricha was, at this stage, distinctly 

 recognizable within the cyst, which after a time gave way 

 and liberated an organism -^\-^' in length, containing 

 dirty-looking granules similar to those of the speci- 

 mens of Oxytricha already existing in the water {rn). 

 Although organisms of this kind were produced from the 

 majority of the vesicles, in others, which appeared in 

 every way similar, the embryo mass, owing to some 

 unknown cause, was seen to shape itself into the form 

 of a Plassconia having four or five very deep and longi- 

 tudinal dorsal depressions. These embryos ultimately 

 moved about with extreme activity within their cysts. 

 Occasionally also another form of Pl^sconia was pro- 

 duced whose dorsal shield was slightly convex and 



