X ON THE STUDY OF BIOLOGY 283 



sort of knowledge which can be gained only in 

 this practical way, his exploits as a tea merchant 

 will soon come to a bankrupt termination. The 

 " paper-philosophers " are under the delusion that 

 physical science can be mastered as literary ac- 

 complishments are acquired, but unfortunately it 

 is not so. You may read any quantity of books, 

 and you may be almost as ignorant as you were 

 at starting, if you don't have, at the back of your 

 minds, the change for words in definite images 

 which can only be acquired through the operation 

 of your observing faculties on the phenomena of 

 nature. 



It may be said : " That is all very well, but 

 you told us just now that there are probably some- 

 thing like a quarter of a million different kinds 

 of living and extinct animals and plants, and a 

 human life could not suffice for the examination 

 of one-fiftieth part of all these." That is true, 

 but then comes the great convenience of the way 

 things are arranged ; which is, that although there 

 are these immense numbers of different kinds of 

 living things in existence, yet they are built up, 

 after all, upon marvellously few plans. 



There are certainly more than 100,000 species of 

 insects, and yet anybody who knows one insect 

 if a properly chosen one will be able to have 

 a very fair conception of the structure of the 

 whole. I do not mean to say he will know 

 that structure thoroughly, or as well as it is desir- 



