OE, THE HOME-CULTURE OF FEESH-WATEE PLANTS. 



After the reading of the foregoing paper, it was 

 remarked by Professor Balfour that the motions in 

 question might be the result of the growth of the cells 

 of the plant ; hut Dr. Lankester considered them en- 

 tirely owing to the proteinaceous protaplasm within 

 the cell, a matter which, hoth in plants and ani- 

 mals, is known to possess a contractile power. It 

 was the source of the movements in the Proto- 

 phyta and Protozoa, and might he regarded as 

 containing the essential elements of a nervous 

 and muscular system. So far Dr. Lankester's 

 argument agrees with the theory of Professor 

 Knowles ; hut he omitted to state whether he con- 

 sidered the movements voluntary or not, so that 

 this interesting physiological question is still an 

 open one. 



It will he seen, from these observations, that the 

 keeping of an Aquarium should always be accompa- 

 nied by the possession of a microscope, with the aid 

 of which it is evident that an abundant, curious, and 

 instructive course of investigation need never flag, 

 while the inmates of the tank are kept in that flou- 

 rishing condition, which a proper attention to the 

 principles upon which it is founded cannot fail to 

 secure. 



