THK STATE ENTOMOLOGIST. 165 



by the Berenice butterfly — a species of the same genus and of similar 

 appearance but of darker color — the color of the mimetic Disippus 

 deepens nearly or quite to the tint of the Southern Danais. Thus it 

 is that facts before unintelligible are explained by Darwinism ! 



In a discussion on the difficulties of Natural Selection, which took 

 place in late numbers of the London journal Nature, some ingenious 

 objections have been urged. As many of them have especial refer- 

 ence to the mimicry we have been noticing, a brief summary of these 

 objections will prove interesting in this connection, the more espe- 

 cially as all objections must in the end only serve to strengthen a 

 theory, if that theory is sound. 



Mr. Alfred W. Bennett* undertakes to show upon mathematical 

 -considerations, that Natural Selection could not produce these mini. 

 ■etic forms. He assumes that it would take 1000 steps to enable the 

 normal form of a Leptalis for instance, to pass into the protective 

 form of an Ithoviia; that no change less than one-fiftieth of the whole 

 alteration — L e. 20 steps — would be of any use to the insect, and that 

 the alterations in the early stages, being useless to the animal, would 

 not be preserved, and even if they were, could not be attributed to 

 Natural Selection, but to an accumulation of chances. He reiterates 

 what has already been well shown and acknowledged by Darwinians^ 

 namely, that Natural Selection cannot produce the first change, and 

 .asks with good reason why the same principle that works the first 

 -change should not also work the subsequent changes? He does not 

 -dispute the secondary power of Natural Selection, but believes in an 

 unconscious organizing intelligence which co-operates with it to pro- 

 duce the mimetic results. He endeavors to strengthen his position 

 by showing that there is a close connection between instinct and 

 -mimicry, and ventures the theory that vt the power of mimetism, so far 

 .as is known at present, runs almost parijpassu with the development 

 of the nervous system.'' 



The essay is an able and interesting one, and the arguments are 

 skillful and ingenious. It pays due and just respect to Darwinism 

 and forcibly presents the fact, which no one has denied, that some 

 other power than natural selection acts in producing first change 

 The mathematical argument, however, will have little weight with 

 •those who fully appreciate the changes in Lepidoptera that take 

 place in nature. No entomologist who has had any experience in 

 rearing Lepidoptera will admit with Mr. Bennett that 1000 steps are 

 necessary to produce mimetic resemblance, and when this foundation 

 stone of his objection is taken away, much of his other reasoning 

 which is built upon it becomes weak. Instances of great and sudden 

 variation among butterflies and more particularly among moths are by 



\ature, Vol. UI, pp. 30-33. 



