INFUSORIAL ANIMALCULES. 27 



Dr. Ehrenberg, who always leaves a small proportion of 

 air in the vessel ; judging, therefore, from my own expe- 

 rience, I should conclude that he is more careful than 

 myself as to their conveyance. The only inconvenience I 

 have experienced from keeping the vessels entirely filled 

 with water, during the short time of transporting them 

 home, has arisen from those creatures which appear to live 

 on the surface, attaching themselves to the cork, and 

 remaining so when required to be taken out. Remove the 

 corks as soon as you get home, and place the vessels 

 upright; for which a mahogany stand, furnished with a 

 number of holes adapted for the vessels, will be very 

 convenient. A gauze covering, fitted to the frame, will 

 keep out the dust and blacks, without obstructing the free 

 ingress of air. 



We now proceed to the mode of investigating these 

 minute creatures under the microscope. If the kind to be 

 examined are those which swim freely, and are visible to 

 the naked eye, as the Volvox, Bursaria, and other large 

 Polygastrica, and also the free Rotatoria, take a small open 

 glass tube, such as is described in the Microscopic Ca- 

 binet, p. 236, and select the specimens with 

 it in the manner there recommended. The 

 figure of the tube I here insert from that 

 work. The diameters of these tubes may 

 vary from one-eighth to one -twelfth of an 

 inch, and their length from four to six inches. 

 It may be useful occasionally to draw out and 

 slightly bend the extremities which are to be 

 immersed in the water. 



When the creatures are more minute than 



