THE PATH OF EVOLUTION 



The mode of reproduction of Bacteria by division 

 of the cellules with or without the formation of 

 nuclei or spores has already been described. Among 

 the next higher order, the lower Algae, reproduction 

 is often, even in the same individual, both asexual 

 and sexual. In the tube-shaped Vaucheria Clavata 

 the non-sexual process, viewed under the microscope, 

 is curious and interesting. The tube-like structure 

 of the plant terminates with rounded ends; close 

 thereto a cellule several times longer than its 

 diameter is formed. The chlorophyll granules form 

 in the plasmodium contents, and partly fill the cell. 

 A few hours later the cell bursts through the end of 

 the tube. It now forms an ovoid body, dark green 

 at one end and nearly colorless at the other. It 

 parts from the parent plant and swims away in the 

 surrounding water, apparently seeking a suitable 

 place for lodgment, avoiding floating matter or other 

 obstacles in its path. It stops at times, apparently 

 to rest ; resumes its course soon again. Its motion 

 forward is at the rate of about three-quarters of an 

 inch in a minute, though seemingly rapid under a 

 miscroscope, crossing the field of vision in less than a 

 second ; it revolves on its longer axis and progresses, 

 therefore, with a spiral, screw-like motion. This is 

 produced by the ciliated or eyelash-like extensions, 

 that issue from its gelatinous substance in all direc- 

 354 



