108 MICROSCOPIC ILLUSTRATIONS. 



which deposit them on the sides of vessels, &c. &c., fall 

 within the above description. 



In examining any of these, this apparatus will be found 

 to be exceedingly convenient and useful j for, by its aid, 

 we can with perfect facility carry our researches into the 

 contents of any open vessels, or phials, of a size propor- 

 tionable to the range of the holder. In the ordinary way, 

 a phial or vessel, unless it be very shallow indeed, must 

 be turned upon its side, and stopped with a cork to pre- 

 vent the water from running out ; and even then it often 

 happens that a portion of the air included in the vessel 

 presents itself in the field of view, so as greatly to dis- 

 concert our plans. In using the spring-phial-holder, 

 however, this inconvenience is avoided : and there is, 

 besides, a more considerable advantage to be derived 

 from it, viz. that of not disturbing the objects, by turn- 

 ing them about, so as to accommodate them to the micro- 

 scope. Again, as open vessels can be put in the holder 

 with as much readiness as an ordinary slider can be placed 

 on a common stage, a series of observations on the con- 

 tents of different vesels may be made in a very short 

 space of time. In viewing by common means the cyclosis 

 in aquatic plants, such as those of the order Characea, 

 where every cell throughout the plant has its distinct cir- 

 culation, it is necessary that a small portion of the plant 

 should be severed from the rest, placed in a slider, and 

 covered with a plate of mica or glass. This section will 

 not of course remain alive for any great length of time, 

 unless it be carefully replaced in a large vessel. With 



