BATES'S AND F. MULLEE'S THEOEIES 119 



exposed surface, black behind for the remaining 

 third. They are undoubtedly protected by quali- 

 ties which make them excessively unpalatable 

 to the bulk of insect-eating animals. Some ex- 

 perimental proof of this has been obtained by 

 Mr. Guy Marshall. What are the forms which 

 surround them? According to the hypothesis 

 of Bates they would be, at any rate mainly, pala- 

 table hard-pressed insects which only hold their 

 own in the struggle for life by a fraudulent imita- 

 tion of the trade-mark of the successful and 

 powerful Lycidae. According to Fritz Miiller's 

 hypothesis we should expect that the mimickers 

 would be highly protected, successful and abun- 

 dant species, which (metaphorically speaking) have 

 found it to their advantage to possess an adver- 

 tisement, a danger-signal, in common with each 

 other, and in common with the beetles in the 

 centre of the group. According to the first view 

 the mimic is a danger to its model, according 

 to the second it is a benefit. If A, B, C, D, &c., 

 are all unpalatable and all recognized by the same 

 appearance, and if their enemies have to learn by 

 experience what to eat and what to reject, it 

 follows that when A is tasted and found un- 

 pleasant, B, C, D, &c., are benefited. They would 

 be tasted more cautiously, or perhaps abandoned 

 without tasting. On the next occasion B might 

 be tasted by some other inexperienced foe, and 

 the advantage would lie with A as well as C, D, 

 &c. It is hardly necessary to explain that under 



