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} 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 pro- 

 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 Charace&y 

 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 



