124 MICROSCOPIC OBJECTS. 



exhibit this phenomenon. The following aquatic plants 

 are generally transparent enough to show the circulation 

 in every part of them : — Nitella liyaVma, Nitella trans- 

 lucens, Chara vulgaris, and Caulinia fragilis. In the 

 Frogbit (Hydrocharis) it is best seen in the stipulse of 

 the leaves and the ends of the roots. The magnifying 

 power suited for the above are between 60 and 200 

 diameters. In the Spiderwort (Trades cantia virginica) it 

 is seen in the bead-like filaments surrounding the stamens 

 of the flower. Power 300 to 400 diameters. In the 

 Common Groundsel {Senecio vulgaris) it is said to be seen 

 in the hairs surrounding the stalks and flowers. In the 

 Valisnaria spiralis circulation may be seen in sections of 

 the leaf." 



Among Infusoria the genera Closterium, Navicula, 

 and Euastrum exhibit a curious circulatory motion. 



Ciliary Currents. — The respiratory organs, or more 

 properly the organs for aeration of the circulating fluids, 

 in the MoUusca and some other classes of animals, are 

 furnished with cilia. These ciha (which resemble very 

 minute eyelashes, from whence their name is derived) 

 form a fringe around the bronchi, and are in constant 

 motion ; the purpose of which is to bring a fresh supply 

 of water into contact with the organ by which the oxygen 

 is obtained. The exhibition of this process yields to none 

 in interest, except indeed the actual circulation of the 

 vital fluid itself. For observing this phenomenon, arm 

 your microscope with an object-glass of one third of an 

 inch focus, the power being about 100 diameters. Take 



