NEW ORGANISMS 



295 



blood plasma. The chill that accompanies this disease takes 

 place just at the time when the spores are being discharged. 



342. Swimming spores. In many of the algae, cells may 

 break up into a number of spores (usually four), but these 

 differ from the spores of the fungi in having rather thin walls 



FIG. 128. Swimming spores 



In many of the chlorophyl-bearing water plants that do not produce seeds (algae), swim- 

 ming, or swarm, spores are produced. /, Chondrioderma difforme ; 2, Conferva bombycina; 

 3, Botrydium granulatum; 4, Haematococcus pluvialis ; j, Chlorosphaera limicola 



and in being provided with cilia, by means of which they swim 

 about in the water, suggesting minute animals (Fig. 128). 



343. Cysts. There is still another kind of cell that may 

 be classed with the spores. This is formed by many protozoa 

 when the conditions for their usual activities are in some way 

 unfavorable. The protoplasm shrinks into a round mass, and 

 a thick cell wall, or cyst, is formed. In this encysted condition 

 the protoplasm may rest for an indefinite time, resisting the 

 unfavorable conditions. The animal may thus survive winters 

 or droughts, or perhaps escape destruction when taken into 

 the food tube of a large animal. 



