606 THE MICROSCOPE. 



vestigated the subject more closely for himself, and finds 

 that, in place of being forty-eight species, the whole are 

 nearly identical with the yeast fungus, and that one will 

 produce the other. See the " Microscopical Journal," 

 April, 1859. 



P. 223.] The motion of the sap in the chara and 

 other vegetables has been explained on the principle of 

 osmose and exosmose. A fluid of lower density (water) 

 chemically acts on and penetrates membranous tubes 

 containing a liquid of greater density (sap or chlorophyl) ; 

 that fluid which begins the flow into the tubes may sustain 

 it in continued current through them, so long as a differ- 

 ence in density and composition between the water and 

 sap is maintained. A similar principle, doubtless, aids 

 the motion of fluids in the animal body in some instances; 

 in others the movements observed (as in the air-tubes, 

 &c.) have been traced to the vibrations of cilia, and are 

 therefore no proof of the existence of vital attractions and 

 repulsions. 



P. 233.] At page 233 I state that it is futile to expect 

 to prove that crystals are the possible transition of the inorganic 

 to ORGANIC MATTER. In correction, I beg to call attention 

 to the highly valuable contributions of Mr. George Rainey, 

 who has pointed out the remarkable fact that many of the 

 appearances presented by the hard structures of animals, 

 and which had been usually referred to cell-development, 

 are really produced by the physical laws which govern the 

 aggregation of certain crystallizable salts when exposed to 

 the action of vegetable and animal substances in a state of 

 solution. The importance and interest of this subject can 

 hardly be overrated. I therefore subjoin Mr. Rainey's 

 process for obtaining artificial calculi : 



" The chemical substances to be employed in the pro- 

 duction of the artificial calculi are, a soluble compound 

 of lime, and carbonate of potash or soda, dissolved in 

 separate portions of water ; and some viscid vegetable or 

 animal substance, such as gum or albumen, to be mixed 

 with each of these solutions. And the mechanical con- 

 ditions required to act in conjunction with the chemical 

 means are, the presence of such a quantity of the viscid 



