300 MOVEMENT 



arranged in regular rows, and capable of ramifying 

 in different directions. Some of these cells at certain 

 times are quite full of protoplasm, and in a photograph 

 appear as a dark mass, limited by a transparent 

 cellulose membrane. 



Later on, the cells evacuate their contents more or 

 less completely ; they are then seen to be reduced to 

 a transparent membrane which is indicated in a 

 photograph as a clear outline. Concerning this 

 phenomenon, botanists have discovered one of the most 

 extraordinary facts in organic life. The protoplasm 

 which at first completely fills the cells as a homo- 

 geneous amorphous mass becomes aggregated, and 

 breaks up into a number of portions, each of which 

 develops at one or other extremity a pair of vibrating 

 cilia. 



These units take an independent movement, but as 

 long as they are encapsuled within the cell the move- 

 ment is feeble. As soon, however, as part of the cell 

 wall ruptures, the small bodies escape through the 

 opening and swarm about outside in the water by 

 means of their vibrating cilia. The little bodies are 

 zoospores ; it is generally at sunrise that the escape is 

 effected, and the movements during the first hours of 

 freedom are very active. 



The movements of the zoospores may be followed 

 throughout by observing in a series of photographs 

 the successive positions they occupy in the mother 

 cell. But no adequate description could be given 

 to those, who have never watched the phenomenon, of 

 the activity which reigns within the cell, and only 

 ceases when all the zoospores have succeeded in 

 effecting their escape. 



The Use of the Solar Microscope in Chronophoto- 

 graphy. — The practical application of the method 

 which has just been described presents some difficulty 



