Protozoa and Rotifera at Havana, III. 311 



balsam were made on the slide by the irrigation process, that 

 is, by placing a drop of the liquid on the slide at the edge of 

 the cover-glass, and then drawing it under the cover-glass 

 by means of blotting-paper. The Tokophrya was attached to 

 Opercularia, and many of the latter genus were killed well 

 expanded, thus suggesting the idea that this method could 

 probably be used with good results for other Vorticellidce. 



GEOGKAPHICAL DISTRIBUTION. 



There is probably no place on earth, unless it be a sandy 

 desert or a subterranean stream, where Protozoa may not be 

 found. No stream is too clear or pond too muddy for them 

 to thrive in. They are found in the warm waters of the 

 tropics and in the icy waters of the northern countries. The 

 United States stands next to Europe in the number of recorded 

 species. A considerable number are also found in Australia. 

 There are many cosmopolitan species, which is not so re- 

 markable when we consider that the light cysts may very 

 readily be carried long distances by air currents. 



FOOD RELATIONS. 



But little attention has been paid to the food of the Proto- 

 zoa, and it is very desirable that students should make and 

 record careful observations along this line. 



In general it is known that Amosha, Arcella, Diffiugia, Vor- 

 ticella, Opercularia, and the like, feed largely on diatoms and 

 desmids, diatoms especially seeming to be a favorite food 

 of such forms as Vorticella and Opercularia. Euglena has 

 been found within the body of Opercularia, and Tokophyra 

 and Acineta are predaceous, living upon other Protozoa. 



Individuals of the latter genus have been seen to kill and 

 devour Vorticella. Schewiakoff ('93) says that' rotifers, 

 daphnids, and Chcetonotus also serve as food for Protozoa. 

 No doubt many of the species that possess chlorophyll derive 

 some nourishment from gases, as plants do ; while other 

 forms absorb organic matter in solution in the water. It is 

 probably true that plants constitute a larger proportion of 

 their food than animals, but the data on this point are so 

 meager that no general statement can be made. 



