THE PLASTIC BEHAVIOR OF ANTS. 537 



pathy, but the observations of most myrmecologists have yielded only 

 doubtful results. My own observations are negative, except in a single 

 instance. Several years ago I kept a large colony of Eciton schinitti 

 in a Lubbock nest surrounded by a water moat. Workers repeatedly 

 fell into the water and on several occasions I saw other workers reach 

 down and pull them out. Forel, Lubbock and Wasmann relate instances 

 of ants nursing and caring for crippled or mutilated companions. But 

 if we reject all such observations as too infrequent or doubtful to have 

 any value, there still remain a great many easily observed cases that 

 can be explained only on the supposition that ants respond quickly by 

 imitating the purposeful activities which they perceive in their nest- 

 mates. The stimulus in these cases would seem to be highly individ-- 

 ualized, to use Driesch's expression, and entirely unlike those which 

 call out reflex and instinct actions. By certain critics of the general 

 position here taken much has been made of the numerous cases in 

 which ants of the same colony work at cross-purposes, or in opposition 

 to one another. Such cases naturally arise on account of the powerful 

 initiative of the individual ants, but they eventually resolve themselves 

 into cooperation, or, at any rate, into a lack of opposition, through a 

 weakening or reversal of the tactics of one of the contending parties, 

 These contentions are, in fact, merely slight temporary disturbances or 

 maladjustments analogous to those which are continually occurring 

 among the different organs and tissues of a Metazoan body. 



5. Docility. Although the facts recorded in the preceding para- 

 graphs indicate very clearly that ants are capable of learning by expe- 

 rience, and that they must, therefore, possess memory, this becomes 

 even more evident when it is shown that they can actually be trained 

 like many of the higher animals. Wasmann (1899(7) succeeded in the 

 course of a few days in training workers of Formica rnfibarbis and 

 fusca to come for food to his finger, from which they at first fled. 

 Ernst (1905) obtained similar results with a fusca worker, which he 

 taught to come out of a test-tube and take food from his finger while 

 it was in motion. Turner (1907^) has recently described some experi- 

 ments in which Myrmica punctiventris and F. subsericea trained them- 

 selves to drop from a stage with a pupa and to carry it to the nest. 

 These ants then permitted him to replace them on the stage with a 

 pair of tweezers. This act was repeated over and over again. More 

 interesting is the following experiment in which he taught F. subsericea 

 to use a section lifter as an elevator on which to pass to and from a 

 stage connected with an island nest by an incline : " On this occasion 

 two marked workers, A and B, were being experimented upon at the 

 same time. The one I have called A readily learned the way down 



