1872.] 



Modes of Origin of Infusoria fyc. 



261 



thickly studded with the most distinct egg-like bodies, varying in size 

 from 5^-o"-3 5 a " iu diameter. What struck me more than any thing was 

 the extreme distinctness with which almost all the phenomena described 

 by M. Pouchet were to be seen. There could be little room for doubt with 

 such objects before one. 



The only difficulty was to make out exactly what was the nature of the 

 first change by which the egg-like body became differentiated from the 

 surrounding substance of the pellicle. I laboured under some disadvan- 

 tages from having to examine an old and somewhat opaque pellicle ; but 

 after the most careful and repeated observations with reference to this 

 point, I have been led to adopt an opinion slightly different from that of 

 M. Pouchet. Instead of small concentrations of granules occurring 

 which gradually increased in size and at last became enclosed by a bound- 

 ing membrane, it seemed to me that the differentiation took place after a 

 manner essentially similar to that by which an ordinary " embryonal area " 

 is formed*. The small embryos did not appear to represent the earlier 

 stages of large embryos ; and it seemed rather that spherical masses of the 

 pellicle of different sizes began to undergo molecular changes, which termi- 

 nated in the production of Paramecia of a correspondingly different bulk. 



Fig. 8. — Mode of Origin of Paramecia. ( X 800.) 



a. First stage of differentiation. 



b. Later stage, in "which a vacuole has appeared. 

 b'. Similar stage of much larger embryo. 



b". Another embryo, which has segmented into four (only three parts visible). 



c. Later stage : embryo filled with large particles and revolving -within its cyst. 



d. Paramecium after it emerges from its cyst. 



e. Nassnla-l\ke form into which many afterwards passed. 



* On the other hand, the embryos of unknown organisms which wero seen to form in 

 the infusion of turnip-leaves did seem to develop in a manner remarkably similar to the 

 embryos of Paramecium viride, as described by M. Pouchet. 



VOL. XX. U 



