228 



AQUATIC MICROSCOPY FOR BEGINNERS. 



floating particles roughen it by adhering to 

 the outer surface. The animal living within 

 it is colorless. The ciliary disk is divided 

 into two lobes, which she folds together 

 when frightened and forced to retire to the 

 lower regions of her domicile for protection. 

 The sheath is secreted from the body 

 of the occupant. It is not built up of par- 

 ticles picked out of the currents that flow 

 from the ciliary discs; neither is it, as with 

 some forms, composed of fsecal matter. 



Limnias is not rarely found attached to 

 the leaflets of Ceratophyllum, and is proba- 

 bly named Limnias ceratophylli for that rea- 

 phyiii. son, although it is almost as often to be 

 obtained from Myriophyllum. 



There is another species of Limnias also rather 

 common in the writer's locality, but which differs from 

 Limnias ceratophylli in having the sheath apparently 

 formed of narrow rings, so that the edges, as seen un- 

 der the microscope, seem finely waved or scalloped. 

 By this character it may be easily distinguished from 

 L. ceratophylli. It is named Limnias annuldta. 



7. Megal6trocha (Fig. 160). 



The clusters formed by Megaldtrocha are not rarely 

 so large that they become visible to the naked eye as 

 little whitish masses clinging to the leaflets of Myrio- 

 phyllum, which it seems to prefer. With the pocket- 

 lens the indiv'dual Rotifers may be seen rising and 

 bobbing about as they expand or contract, but a low 

 power of the compound microscope is needed to ap- 

 preciate their beauty. The expanded body is some- 



