INSTINCTIVE, EMOTIONAL AND REFLEX ACTION 349 



subsequently showed exactly what happened by some 

 very ingenious experiments. 



"He took some of the crickets and introduced poison into 

 their bodies with a needle. When this was done indis- 

 criminately, that is, in no particular part of the animal's 

 body, it either killed the animal or produced very tem- 

 porary results, according to the amount of poison intro- 

 duced. When, however, he introduced the needle into the 

 three nervous centres (thoracic ganglia) which control 

 the movements of the insect, he found that complete par- 

 alysis ensued. More than this, the metabolism was 

 checked, and the paralyzed insect continued to live with- 

 out food for several weeks, which it certainly could not 

 have done under normal conditions. An interesting point 

 about this instinct of Sphex is that the prey is stung in 

 one particular point where the tissues are soft and the 

 nerve centres are easily reached from the surface. Much 

 the same thing happens in the case of Ammophila and its 

 prey, the caterpillars, only here the wasp has to apply its 

 sting many times, so that all the middle segments, at 

 least, of the animal's body are paralyzed. 



"Now the supporters of the theory that acquired char- 

 acters are transmitted say that it is impossible to account 

 for the origin of these instincts in any other way than 

 that the ancestors of the existing wasps first exercised a 

 certain amount of intelligence. A wasp found that when 

 it stung a grasshopper in a particular place, that grass- 

 hopper was paralyzed and was much more easily carried 

 to the nest. It remembered this, and led by past exper- 

 iences, always stung its prey in the same place. This 

 habit produced an effect on the germplasm, and the off- 

 spring tended to sting their prey in the same manner 

 until the instinct became established, and so no longer 

 depended upon the intelligent action of the wasp. This 



