180 



A COURSE ON ZOOLOGY. 



Like the corals, sponges fix themselves on submarine 

 rocks; they are found in all seas, but those from the Medi- 

 terranean, and particularly those of the Archipelago, are 

 most esteemed. The preparation of the sponges is very 

 simple, consisting of washing them many times in fre- 

 quently renewed fresh water. In this manner they are 

 freed from their gelatinous envelopes and the foreign 

 matters distributed through their tissue. 



CHAPTER XX. 

 Protozoa Infusoria Microbes. 



THE protozoa are animals of extremely simple organ- 

 ization, and most generally of a microscopic size. They 



FIG. 107. 



FIG. 108. 



PAKAMECIUM AUEELIA. COLPODA. 



STENTOR. BURSARIA VORTICELLA. 



