414 THE BEGINNINGS OF LIFE. 



division d'autres organismes, qu'ils sont une impasse et 

 la fin d'une serie vitale et rarement une forme de tran- 

 sition (Micrasterias, Arthrodesmus, etc.).' 



Amongst the many special instances illustrating the 

 truth of his views which are mentioned by Dr. Gros, 

 there is one to which I will now call special attention, 

 as I have quite recently observed transformations of an 

 almost similar nature. 



Green cell-like bodies which had taken origin from 

 a Moss-leaf were, after a time, seen by Dr. Gros to 

 become converted into colourless specimens of Actino- 

 phrys. These increased in size, and ultimately retracted 

 their rays previous to developing cilia and becoming 

 converted into one or other of the forms of Ciliated 

 Infusoria i. Other specimens of the same cells under- 

 went repeated subdivision, and their segments assumed 

 the form of Arthrodesmus (see Fig. 85, h). Some of 

 these four-segmented bodies were afterwards seen to 

 separate into their elemental parts, and each of them 

 divided obliquely (7) so as to form two ellipsoidal 

 corpuscles, which speedily developed into some of the 

 endless forms of Naviculae 2. 



My own observations were as follows: — Having 



^ Loc. cit, pp. 452 and 501. 



2 On the other hand, Arthrodesmus, Micrasterias, and other Pediastreae, 

 whatever may have been their origin, are said by Dr. Gros to lapse into 

 the confervoid mode of growth whenever they are placed upon a damp 

 soil (loc. cit., p. 452). At p. 311 Dr. Gros also speaks of the origin of 

 Arthrodesmus from the fission-products of Euglenae, and of these being 

 converted in the manner above stated into Naviculae. 



