n8 THEORIES OF EVOLUTION 



those caterpillars which are impelled by their nervous 

 system to make ill-formed, conspicuous cocoons have no 

 chance of living, and, in the perfect stage, of producing 

 offspring. Hence, the selection caused by the keen sight 

 of foes first raises and then maintains at a high level the 

 standard of cocoon-making. 



This contention as to the uselessness and danger of 

 experience applies to the whole of those smaller defenceless 

 animals which, when once they have been detected, have 

 no chance of fighting with their enemies and but little of 

 escaping. 



Another special kind of instinct has been greatly relied 

 on by Romanes as evidence for the Lamarckian Theory 

 of transmitted experience. Certain Hymenoptera allied 

 to wasps, the Fossores or sand-wasps, possess an instinct 

 which leads them to sting larvae and store them up in 

 their nests as food for their young. It is generally be- 

 lieved that the larva is stung in the central part of the 

 nervous system so that it can no longer struggle. I say 

 ' generally believed ' because it has been pointed out to 

 me by so distinguished an observer as Dr. G. W. Peck- 

 ham of Milwaukee, that certain facts are opposed to the 

 generally received account. 1 It is to be hoped that the 

 observations, which are chiefly due to Fabre, will be 

 repeated and tested as minutely as possible. The prey 

 is stored up in the mud-tube or burrow of the Hymeno- 

 pteron, and keeps perfectly fresh because it is alive, 

 although completely paralysed. Larvae stored up in this 

 way appear to live much longer than those which, in the 

 full possession of their faculties, are deprived of food. 



Now this is a very wonderful instinct, which, it has been 

 argued, cannot be explained except on Lamarckian lines. 

 I maintain, on the contrary, that it is a case which cannot 

 by any possibility be explained by the Lamarckian Theory. 



1 My friends Mr. and Mrs. Peckham have now published their 

 valuable researches upon the habits of the Fossorial Hymenoptera in 

 two works, which are a mine of information on this fascinating subject. 

 George W. Peckham and Elizabeth G. Peckham, On the Instincts and 

 Habits of the Solitary Wasps; Wisconsin Geological and Natural History 

 Survey: Madison, Wis., U.S.A., 1898. Wasps Social and Solitary. 

 Boston and New York, 1905. 



