OF CILIATED INFUSOEIA 275 



die in this way I could not discover ; and in various attempts that 

 have since been made I have never succeeded in annuUing the 

 hfe of the Hydatinse without destroying the vitality of their eggs. 



On another occasion a living Otostoma was found within the 

 body of a dead Hydatina under the following circumstances. I 

 had a stock of these Rotifers in confinement for twelve days, and 

 the vessel in which they were contained had been standing on the 

 mantelpiece of my study, under a bell-jar, for the greater part of 

 that time. Much evaporation of the fluid had taken place, and 

 no distilled water had been added to compensate for the loss. On 

 examination I found, mixed with the Euglenas on the surface, 

 numerous amorphous saline concretions resulting from the 

 evaporation ; also ' resting eggs,' and many ordinary black-granule 

 eggs, together with Hydatinze containing eggs of each variety. 

 I took up an isolated batch of these eggs, in association with some 

 Eugleme, two or three of the Rotifers, and some of the saline 

 concretions, and placed them in a drop of distilled water under a 

 cover-class. On examining this specimen with the microscope 

 I found that several of the eggs seemed to be freshly laid, so I 

 resolved to try whether a transformation of any of them could be 

 brought about under the cover-glass — which was prevented from 

 pressing upon the eggs by the presence of the saline concretions. 

 I accordingly placed a shallow layer of water on the wrong side of 

 one of a pair of ' tinting saucers,' ^ placed the microscope slip 

 within it, and over it the other saucer right side downwards : the 

 two together making an excellent damp chamber, with a very 

 limited air space, in which the specimen would be cut off from 

 light rays of all kinds. 



When the specimen was looked at, after the expiration of three 

 days, about one-third of the water beneath the cover-glass had 

 evaporated, but on examination with the microscope I found three 

 great Otostomas revolving within unruptured egg-cases ; and, 

 within the body of a dead Hydatina, which was only partially 

 decayed, so that its integument was quite whole and remains of 

 its internal organs were distinct, was a great Otostoma densely 

 filled with black granules, free, and moving about in a very active 

 manner. The whole body of the Rotifer, when thus seen, was 

 visible, but unfortunately, after running a weak osmic acid solution 



' Made of white earthenware, about four inches in diameter, and obtainable 

 from Messrs. Swift and Son, of 8i, Tottenham Court Road. 



