The experiment just described to show the importance of the tendency to turn in a certain direction was the first one of the first series after the change in conditions.  When given its second chance in this series the subject escaped directly by the Left passage in 33 seconds, and for the three following trips the time was respectively 25, 25 and 30 seconds.

Upon the experimental evidence presented we base the conclusion that crawfish are able to profit by experience in much the same way that insects do, but far more slowly.

[Illustration:  FIG. 4.  Path taken by crawfish which had been trained to avoid the Left passage, when the Right passage was closed.  Showing turning to the right as in Fig. 3.]

It was thought that a study of the way in which crawfish right themselves when placed upon their backs on a smooth surface might furnish further evidence concerning the ability of the animals to profit by experience.

Dearborn[3] from some observations of his concludes that there is no one method by which an individual usually rights itself, and, furthermore, that the animals cannot be trained to any one method.  His experiments, like Bethe’s, are too few to warrant any conclusions as to the possibility of habit formation.

   [3] Dearborn, G.V.N.:  ’Notes on the Individual Psychophysiology
   of the Crayfish,’ Amer.  Jour.  Physiol., Vol. 3, 1900, pp.
   404-433.

For the following experiments the subject was placed on its back on a smooth surface in the air and permitted to turn over in any way it could.  Our purpose was to determine (1) whether there was any marked tendency to turn in a certain way, (2) whether if such was not the case a tendency could be developed by changing the conditions, and (3) how alteration in the conditions of the test would affect the turning.

A great many records were taken, but we shall give in detail only a representative series.  In Table III., 557 tests made upon four subjects have been arranged in four groups for convenience of comparison of the conditions at different periods of the training process.  Each of these groups, if perfect, would contain 40 tests for each of the four subjects, but as a result of accidents II., III., and IV. are incomplete.

TABLE III.

RE-TURNING OF CRAWFISH.

Group.  Number of    L.    R.   Time in   Tests. 
Animal.       Per cent.   Seconds. 
I.       2         22.5  77.5    14.6     40
3         42.5  57.5     2.6     40
4         52.8  47.2     4.3     38
16         44.5  55.5    22.5     45
—­         ——­  ——­    ——­    —–­
40.6  59.4    10.8    163

Group.  Number of    L.    R.   Time in   Tests. 
Animal.       Per cent.   Seconds. 
II       2         28    72      50       43
3         32    68       6.2     50
4         —­   100       6.8     40
16         31.3  68.7    39.3     42
—­         ——­  ——­    ——­    —–­