206 MICROSCOPY FOR BEGINNERS. 



times, however, they are covered with short spines or 

 hairs. 



It is a curious fact that although there are male and 

 female Eotifers, the males are seldom seen. In some 

 species they have never been found, and are therefore 

 entirely unknown. Those that have been discovered 

 are much smaller than the females of the same species. 

 They are always free-swimming, and are without a mas- 

 tax and alimentary canal, or with the latter so imperfect 

 that it is useless. Male Rotifers, therefore, never take 

 food. It is not probable that the beginner will meet 

 with them, or at least will recognize them as the 

 males. 



This group of animals is almost as common and abun- 

 dant as the Infusoria, and they are found in similar 

 places. They are specially fond of hiding in masses of 

 Ceratophyllum. Indeed, almost any pond or shallow 

 body of still water may be examined with a certainty 

 of finding them. They have even been sparingly ob- 

 tained from the moss that grows between the bricks in 

 damp pavements. Some species develop in vegetable 

 infusions, but as a rule they prefer fresh water. The 

 beginner will, of course, not expect that all the genera 

 and species will be included in this little book. He will 

 obtain very many whose names he cannot hope to learn. 

 He can, however, know them to be Rotifers by the pres- 

 ence of the mastax, which makes them one of the most 

 easily recognizable groups of microscopic animals. They 

 form an interesting class of creatures for microscopic 



