598 THE POPULAR SCIENCE MONTHLY, 



these other heads of evidence had reference to the theory concerning 

 the causes of transmutation, this head of evidence has rcfei'ence to the 

 fact of transmutation. Whatever, therefore, we may think concern- 

 ing the evidence of the causes, it is quite distinct from that on which 

 I now rely as conclusive proof of the fact. 



I shall now, for the sake of fairness, briefly allude to the more im- 

 portant cases of special difiiculty which lie against Mr. Darwin's theory 

 of the origin and development of instincts. For the sake of brevity, 

 however, I shall not allude to those cases of special difficulty which he 

 has himself treated in the " Origin of Species," but shall confine my- 

 self to considering the other and most formidable cases which, after 

 surveying all the known instincts presented by animals, I have felt to 

 be such. 



First, we have the alleged instinct of the scorpion committing sui- 

 cide when surrounded by fire. This instinct, if it really exists, would 

 no doubt present a difficulty, because it is clearly an instinct which, 

 being not only of no use, but actually detrimental both to the indi- 

 vidual and the species, could never have been developed either by 

 natural selection or by lapsing intelligence. I may, however, dismiss 

 this case with a mere mention, because as yet the evidence of the fact is 

 not sufficiently precise to admit of our definitely accepting it as a fact. 



There can be no such doubt, however, attaching to another instinct 

 largely prevalent among insects, and which is unquestionably detri- 

 mental, both to the individual and to the species. I allude to the in- 

 stinct of flying through flame. This is unquestionably a true instinct, 

 because it is manifested by all individuals of the same species. How, 

 then, are we to explain its occurrence ? I think we may do so by con- 

 sidering, in the first place, that flame is not a sufficiently common ob- 

 ject in nature to lead to any express instinct for its avoidance ; and in 

 the next place by considering that insects unquestionably manifest a 

 disposition to approach and examine shining objects. Whether this 

 disposition is due to mere curiosity, or to a desire to ascertain if the 

 shining objects will, like flowers, yield them food, is a question which 

 need not here concern us. We have merely to deal with the fact that 

 such a general disposition is displayed. Taking, then, this fact in con- 

 nection with the fact that flame is not a sufficiently common object in 

 nature to lead to any instinct expressly directed against its avoidance, 

 it seems to me that the difficulty we are considering is a difficulty no 

 longer. 



The shamming-dead of insects appears at first sight a formidable 

 difficulty, because it is impossible to understand how any insect can 

 have acquired the idea of death or of its intentional simulation. This 

 difficulty occurred to Mr. Darwin thirty or forty years ago, and among 

 his manuscripts I find some very interesting notes of experiments upon 

 the subject. He procured a number of insects which exhibited the in- 

 stinct, and carefully noted the attitude in which they feigned death. 



