198 JAX B. DEMBOWSKI. 



described above, where the fiddler had to dig between two glass 

 plates, this exact following of the former track may be easily 

 observed. A female dug a vertical hole (Fig. 3, a) and then the 

 whole apparatus was turned at right angles. The crab changed 

 the direction of the digging (Fig. 3, 6). All the time the burrow 

 remained filled with sand save the end-chamber. On the 

 following morning I found the female out of the apparatus and 

 the hole showed conditions as on Fig. 3, c. The track of digging 

 could be distinctly followed and it corresponds exactly to the 

 previous one. 



Nevertheless such a behavior is not a rule and I have seen 

 many times that the crab may choose an entirely new direction. 

 One individual has dug itself out and the burrow remained open 

 for several hours. Then it entered into it, grasped sand from 

 the bottom and carried it to the opening, closing it in the usual 

 way. Uca then proceeded to work until the whole canal became 

 tightly filled with sand. During the work the end-chamber 

 increased both in volume and length, directing itself obliquely 

 upward but at right angles to the former burrow. After having 

 closed the burrow the crab immediately started again the work 

 of digging itself out in the new direction. It detached pellets 

 from the roof and deposited them at the inner corner of the 

 chamber. After some time a new open burrow was manufactured 

 and as the end-chamber has increased considerably during the 

 previous work it had now room enough for all sand detached 

 from its roof. As a result there was a new open burrow at 

 right angles to the first. I am unable to say what may be the 

 biological significance of such a peculiar behavior. 



We see clearly at least that closing the burrow before high 

 tide and opening it at low tide by no means covers the whole 

 field of the behavior of a fiddler crab. It is merely a scheme 

 under which lies a whole world of varied, complicated and as 

 yet perfectly incomprehensible activities. 



6. The most difficult problem, of course, is the problem of 

 interpretation. I do not know how to characterize the behavior 

 of Uca. Is it reflex, instinct, or intellect? It will be probably 

 safer to speak about the "activities" and it is certainly more 

 important to investigate which are the real properties of those 



