ROTIFERS. 219 



The eggs are usually smooth; sometimes, however, 

 they are covered with short spines or hairs. 



It is a peculiar and interesting fact that although 

 there are male and female Rotifers, the males are sel- 

 dom 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 mastax and alimentary 

 canal, or with the latter so imperfectly developed that 

 it is useless. Male Rotifers, therefore, never take 

 food. It is not probable that the beginner will meet 

 with them, or at least that he will recognize them as 

 the males, or indeed as Rotifers. 



This group of microscopic animals is almost as com- 

 mon and abundant as are the Infusoria, and they are 

 found in similar places. They are specially fond of 

 hiding in masses of Ceratophyllum, or among the 

 leaflets of any aquatic plant. Indeed, almost any pond 

 or shallow body of still water may be examined with a 

 certainty of finding them. They have even been spar- 

 ingly obtained 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. 



A good method by which to capture them for the 

 microscope after a pond-hunting expedition, when we 

 may be sure we have the creatures somewhere in the 

 vessel, is to take a portion of a plant carefully out of 

 the gathering, and rinse it in a watch-glass full of 

 water, preferably in the water which will drip from the 

 plant, or which may be dipped from the collecting- 

 bottle itself. The Rotifera will be sure to be washed 



