GALLS. 149 



Cynips, should cause so singular a divergence from the 

 ordinary growth of the part. The simple puncture 

 and the mere mechanical irritation are not sufficient to 

 explain the phenomenon in a satisfactory manner. I am, 

 therefore, disposed to think, that some acrid secretion is 

 injected from the ovipositor along with the egg, which 

 acting locally, like the vaccine virus, or any other acrid 

 lymph, that in the animal body produces a specific local 

 change in the structure of the part, is the chief cause of 

 the irritation." 



