102 naturalists' assistant. 



debted for the present low state of the microscopical branches 

 of biology. These men without knowing the first requisite 

 of biological work have denounced good instruments and 

 advocated useless ones, have based their opinions of the 

 worth of an instrument on its power of resolving diatoms, and 

 the result is that the beginner, influenced by their dogmatic 

 assertions and widely-copied opinions, has been led to pur- 

 chase an instrument wholly unsuitable for his ends and the 

 result has been discouragement and a cessation of microscopic 

 work. 



