THE ALG^E. 



79 



divide to form sixteen cells covered with a gelatinous 

 envelope, thus producing a new plant similar in all re- 

 spects to the original. 



Volvox globator is another quite common organism. 

 It is a gametophyte. This tiny little organism, which 

 has long been an object of peculiar interest to micros- 

 copists, is the best known plant of its class. It reaches 

 a size just visible to the naked eye, and is found floating 

 on the water in still pools. A good way to look for it 

 is to place quantities of 

 pond weeds and scums 

 in glass dishes, allow 

 them to stand undis- 

 turbed for a time, and 

 then search with a hand 

 magnifier for little green 

 specks rolling through 

 the water. Volvox was 

 long supposed to be an 

 animal; later it was re- 

 garded as a colony of an- 

 imals. Professor Stein, 

 an eminent German bi- 

 ologist, describes it as 

 an animal, in a work 

 published in 1878. Biologists now generally class it as a 

 colony of plants, though some prefer not to express a posi- 

 tive opinion. The colony is spherical in shape, the inte- 

 rior being hollow. The shell of the sphere, so to speak, 

 is composed of a great many little green cells. These 

 cells are larger at one end than at the other, and the little 

 end, which has a pair of flagella, protrudes from the sur- 

 face of the sphere. The colony is motile, the motion 

 being produced by the lashing of the water by the flagella. 

 Under their combined influence the colony rolls or glides 



FIG. 37. Volvox globator, showing the 

 formation of daughter colonies in the 

 interior. 



