The Agassiz Memorials. 247 



world are so complex, so affected by disturbing 

 forces and conditions, that in order to be under- 

 stood, they must first be simplified. The scientist, 

 therefore, by experi7nent^ removes one condition 

 after another, and one disturbing force after another, 

 until the true cause and necessary condition is per- 

 ceived. This is the great method of experhnent^ upon 

 which rests the whole fabric of physics and chemis- 

 try. But when we rise still higher into the field of 

 organised bodies, the phenomena become infinitely 

 more complex and infinitely more difficult to under- 

 stand without the assistance of method, and yet, 

 just here, the method of experiment fails us, or, at 

 least, can be used only to a very limited extent. 

 The conditions of life are so complex, so nicely ad- 

 justed, so delicately balanced, that when we attempt 

 to introduce our rude hands in the way of experi- 

 ment, we overthrow the equilibrium, we destroy the 

 very conditions of our experiment, viz, : life. In 

 this dilemma what shall we do ? Fortunately, nature 

 herself prepares for us a most elaborate series of 

 experiments. The phenomena of life in the higher 

 animals and plants are indeed far too complex to be 

 understood ; but if commencing with these we go 

 down the scale, we find these phenomena becoming 

 simpler and simpler until they reach the simplest 

 expression in the microscopic cell or microscopic 

 spherule of protoplasm. The equation of life is 

 reduced to its simplest terms, and then, only, we 

 begin to find the value of the unknown quantity. 

 This series I will call the natural history series. 

 Again, nature prepares for us another series of ex- 



