VALLISNERIA. 49 



a more intimate knowledge of natural history than 

 most people possess, and in such cases, therefore, all 

 we have to do is to attend to the above general in- 

 structions, until such time as experience will have 

 been able to suggest some other course. Every set 

 of animals and plants has different habits to another, 

 and we should never fall into the error of supposing 

 that because we have been successful with one group, 

 exactly the same treatment cannot fail to be effective 

 with another. To the aquarium keeper as well as 

 to the profound naturalist, the motto of Longfellow 

 equally applies 



" Learn to labour and to wait" 



