242 THE BEGINNINGS OF LIZE. 



observation of which M. Pouchet gives the details 1 , 

 the first rudiments of the eggs began to make their ap- 

 pearance in the pellicle of an infusion of hay on the 

 second day ; on the third day the ovules were distinctly 

 circumscribed, spherical, and -^' in diameter on the 

 fourth day there was no increase of size, the investing 

 membrane could scarcely be recognised, although there 

 was a distinct gyration of the embryo within it, and 

 in those which were most advanced the contractile 

 vesicle could already be discovered; on the fifth day 

 the embryos were found to be of the same size, though 

 slightly greenish in colour, and their movements were 

 more irregular and jerking. At this stage the animalcule 

 had assumed a pyriform shape, fine cilia could be seen 

 on some parts of its surface, and the contractile vesicle 

 was most obvious in the midst of minute and densely 

 packed greenish granules. After a few hours more, the 

 buccal cleft fringed with longer cilia became obvious, 

 and also the so-called nucleus in the centre of the 

 body. The embryos had by this time somewhat in- 

 creased in size, so that after an interval of a few 

 more hours fully developed specimens of Paramecium 

 viride, -f^" in diameter, were swimming about in the 

 solution. 



These observations of M. Pouchet have been repeated 

 by him over and over again. He has thus seen dif- 

 ferent forms of Paramecia arise in the pellicle, and at 

 other times, by steps essentially similar, Kolpod<e have 



1 ' Het^rogenie,' p. 394. 



