40 SEA-SIDE STUDIES. 



want to see, and what no one else can recognise. But 

 this is not the fault of the instrument. So far from 

 the Microscope being in itself deceptive, I maintain 

 that it is less so than the unassisted eye ; and for this 

 reason : all vision is mainly inferential ; from certain 

 appearances certain forms are inferred ; this holds of 

 the eye as well as of the Microscope, the optical prin- 

 ciples of which are essentially the same ; but while the 

 physical conditions are similar, the mental conditions at- 

 tending vision with the assisted and the unassisted eye 

 are different. The microscopic observer is on his guard 

 against fallacies of interpretation which seldom suggest 

 themselves to him when observing with the naked eye ; 

 and this critical caution makes him not only less rash 

 in interpreting appearances, but makes him anxious to 

 verify interpretations by other means. If the contra- 

 dictions of observers be cited as a proof of the decep- 

 tive nature of the instrument, what shall we say to 

 those manifold and persistent contradictions of anatom- 

 ists using their unassisted eyes? But in truth, the 

 controversies of microscopists have rarely turned upon 

 simple facts of appearance, they have been almost 

 wholly questions of interpretation. 



The scientific Naturalist will not content himself 

 with Observation, however cautious and patient ; to it 

 he will add what may be called the great mental in- 

 strument, Experiment, the instrument by which we 

 veinfy the accuracy of our observations and conclu- 

 sions, and by which Nature is interrogated. Experi- 

 mental Physiology is in its infancy ; which is another 



