2l8 AQUATIC MICROSCOPY FOR BEGINNERS. 



with a strong solution of caustic potassa allowed to 

 run under the cover-glass — a small drop at a time. 

 This will dissolve the soft parts, and permit the hard, 

 insoluble mastax to float out, when it can be examined 

 with a high-power objective. Seven kinds or types of 

 these organs are described by microscopical anatomists. 



The Rotifers are reproduced by eggs, which are 

 sometimes hatched within the parent's body, when the 

 animals are said to be ovo-viviparous. This, how- 

 ever, is not common. The eggs are usually semitrans- 

 parent, ovoid bodies, often to be seen on the slide 

 among other matters, with the enclosed Rotifer im- 

 perfectly developed, and the mastax grinding away in- 

 side of the unhatched body, where it cannot possibly 

 have anything to crush. The only parallel to this of 

 which I know is Professor Agassiz's statement that the 

 jaws of the young snapping-turtle snap while the crea- 

 ture is still within the egg. 



The Rotifers may drop their eggs anywhere and 

 leave them to the care of Nature, or they may pru- 

 dently attach them to a leaf or to some other aquatic 

 object. Very often they are adherent to the posterior 

 part of the parent, and are carried about until the 

 young are hatched. In those permanently attached 

 Rotifers that form a soft sheath this is a common oc- 

 currence, and several eggs may at almost any time be 

 seen in the lower part of the lorica, or . adherent to 

 the animal's foot. In such instances, when the young 

 are hatched, they creep up between the parent's body 

 and the side of the sheath, and escape at, the front. 

 They swim about for a short time, and then secrete or 

 build a sheath of their own, which they never volun- 

 tarily leave. 



