30 Journal of the Mitchell Society [Decemhe 



needlelike so as to give them a better hold on their guest and tool. 

 That they are adapted to the latter is evident, yet this adaptation is 

 not such that the crab is likely to be in serious danger when it has not 

 its Actinia. Many of the Melias brought back by explorers are not 

 provided with anemones, and we may believe that the presence of 

 this implement guest is not yet of vital importance to the species of 

 this peculiar genus. The case of the ants which use their larvae as 

 needles is quite different. With them this singular habit is innate 

 and specific. Though probably acquired through intelligent acts, it 

 now belongs entirely to the domain of instinct in the species among 

 which it prevails. And thus we always come back to that predominat- 

 ing fact of the psychological history of arthropods, namely, the trans- 

 formation of intelligent acts into instinctive acts. The following con- 

 siderations formulated by Bergson eminently apply to this group: 



Among animals, invention is never more than a variation on the 

 theme of routine. Locked up as it is within the habits of its species, 

 the animal succeeds no doubt in broadening these by individual ini- 

 tiative; but its escape from automatism is momentary only, just long 

 enough to create a new automatism; the gates of its prison close as 

 soon as they are opened; dragging the chain merely lengthens it. 

 Only with man does consciousness break the chain. 



Man occupies the topmost place in the scale of vertebrates, for, 

 breaking the bonds of instinct he insures thereby the complete expan- 

 sion of his intellect. Insects especially Hymenoptera hold the same 

 dominating position in the scale of arthropods where they are the 

 highest achievement of instinctive life. These two groups represent 

 the actual extremes of the two paths followed by psychic evolution in 

 the Animal Kingdom; the arthropods are going toward instinct, the 

 vertebrates toward intelligence. These two courses are quite op- 

 posite, but why have they diverged? At the beginning of their evolu- 

 tion, during that far distant epoch when they were differentiating 

 along four main lines (echinoderms, moUusks, arthropods, and verte- 

 brates), animals were threatened by a great danger — "an obstacle" 

 says Bergson, "that doubtless almost checked the progress of animal 

 life. There is a peculiarity which we can not help being struck by 

 when we glance at the Paleozoic fauna. The moUusks at that time 

 were more universally provided with shells than those of today. The 

 arthropods in general were provided with a carapace. The oldest 

 fishes had a bony covering of extreme hardness." But "the animal 

 which is shut in a fortress or in a coat of mail is condemned to an exist- 



