THE BEGINNINGS OF LIFE, 249 



imbedded. Gradually the number of homogeneous, 

 biscuit-shaped particles increased, and at last a large 

 vacuole slowly appeared in some portion of the embryo. 

 It lasted for about half a minute, disappeared, and 

 then after a similar interval slowly reappeared. Much 

 irregularity, however, was observed in this respect. 

 The next change that occurred was the complete sepa- 

 ration of the embryo from the cyst which it filled, and 

 the commencement of slow axial rotations. These 

 rotations gradually became more rapid, though they 

 were not always in one direction. The embryo became 

 more and more densely filled with the large biscuit- 

 shaped particles, and at last the presence of cilia 

 could be distinctly recognised on one portion of the 

 revolving embryo. Then, as M. Pouchet stated, the 

 movements grew more and more irregular and impul- 

 sive, so as at last to lead to the rupture of the thin 

 wall of the cyst when the embryo emerged as a 

 ciliated and somewhat pear-shaped sac, provided 

 with a large contractile vesicle at its posterior ex- 

 tremity. 



Sometimes the embryo mass at an early stage of its 

 evolution divided into two or four bodies, each of 

 which developed within the cyst into a perfect em- 

 bryo, and in place of exhibiting a regular rotation, 

 they rolled and tumbled over one another in the 

 most irregular manner. On one occasion I saw a 

 cyst containing two embryos and four spherical Monads 

 about iroW in diameter, the latter having apparently 



