CHAPTER VIII 



AN INSECT VIRUS 



ONE step forward has been taken, but only 

 a very little one as yet, in the problem of 

 the stinging caterpillars. The drenching with 

 ether teaches us that hairiness plays a very 

 secondary part in the matter. With its dust 

 of broken bristles, which the least breath 

 wafts in all directions, it bothers us by depo- 

 siting and fixing its irritant coating upon us; 

 but this virus does not originate in the crea- 

 ture's fleece; it comes from elsewhere. What 

 is the source of it ? 



I will enter into a few details. Perhaps, 

 in so doing, I shall be of service to the novice. 

 The subject, which is very simple and sharply 

 defined, will show us how one question gives 

 rise to another; how experimental tests con- 

 firm or upset hypotheses, which are, as it were, 

 a temporary scaffolding; and, lastly, how 

 logic, that severe examiner, leads us by de- 

 grees to generalities which are far more im- 

 portant than anything that we were led to 

 anticipate at the outset. 

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