5G ON THE EDUCATIONAL VALUE ii 



no one would have dreamt of questioning the 

 propriety of tlie deduction, tliat these creatures 

 have a circulation in one direction; nor would any 

 one have thought it worth while to verify the 

 point. But, in that year, ^L von Ilasselt, happen- 

 ing to examine a transj)arent animal of this class, 

 found, to his infinite surprise, that after the heart 

 had beat a certain number of times, it stopped, 

 and then began beating the opposite way — so as 

 to reverse the course of the current, which returned 

 by and by to its original direction. 



I have myself timed the heart of these little 

 animals. I found it as regular as possible in its 

 periods of reversal: and I know no spectacle in 

 the animal kingdom more wonderful than that 

 which it presents — all the more wonderful that to 

 this day it remains an unique fact, peculiar to this 

 class auiong the whole animated world. At the 

 same time I know of no more striking case of the 

 necessity of the verification of even those deduc- 

 tions which seem founded on the widest and 

 safest inductions. 



Such are the methods of Biology — methods 

 which are obviously identical with those of all 

 other sciences, and therefore wholly incompetent 

 to form the ground of any distinction between it 

 and them.* 



* S.avc for the pleasure of doinp so, 1 need hardly point 

 out my obligations to ^Ir. J. JS. Mill's System uf Loyic, in 

 this view of scientific method. 



