DESMIDS, DIATOMS, AND FRESH-WATER ALG'/E. I07 



spore slowly passes out, being squeezed into an hour- 

 glass shape as it does so. No sooner is it free than it 

 is off like a flash, being covered by rapidly vibrating 

 cilia. But it soon settles down, and finally develops 

 into a filament like the parent. 



In the other method the filament produces from the 

 side, as shown in Fig. 88, a small ovoid cell, and near 

 it a narrow curved or coiled tube. Presently the free 

 ends of each of these cells open, and the contents of 

 the tube pass into the ovoid cell, in which a spore 

 without cilia is finally formed. This spore is said to 

 fall in the mud and to remain unchanged for many 

 months, sometimes all winter, but finally developing 

 into a Vaucheria like the one from which it sprung. 

 In some of the species the ovoid cells are grouped in 

 a cluster of several, and the whole,' with the coiled 

 tube, is raised above the filament on the end of a 

 short Stem. 



7. Ch^tophora (Fig. 89). 



The light-green jelly-like masses into which this 

 Alga grows are found attached to submerged leaves of 



Fig. 89. — Ch2et6phora ^legans. 



