1 86 JAX B. DEMBOWSKI. 



the leg II. strongly bent in the articulation mero-carpopodit 

 comes behind the pellet touching it with the external surface of 

 pro- and dactylopodit. Extending the leg II. in the mentioned 

 articulation the crab pushes and kneads the sand in the same 

 way as do the legs 1-4. A little later also the legs III. and IV. 

 are used in the same manner. Then the large chela begins to 

 play its part. Its lower edge is held closely to the surface of 

 the ground and extending the leg in the articulation mero- 

 carpopodit Uca pushes from time to time large portions of sand 

 away as with a spade. Many authors (Alcock, Pearse) consider 

 the large claw of Uca as being a secondary sexual character. 

 But it plays also an important role in digging. 



The deeper the burrow becomes the higher is the sand hill at 

 its mouth and the greater is the danger that the sand will roll 

 back. All legs, excepting V. and 5, participate in pushing it 

 away and this work is done more and more carefully. At the 

 same time the sand from the deeper layers is more wet and the 

 grains hold together better which facilitates the task. The 

 pellets may be simply rolled away from the mouth of the burrow. 

 In this action again all legs participate and the digging side 

 presents the pellet to the pushing side which rolls it farther. 

 The legs II., III., IV. push the pellet with the external side of 

 their pro- and dactylopodits, the crab walking after it sometimes 

 at a considerable distance. In the field the removed pellets 

 often lie as far as one meter from the mouth of the hole. Some- 

 times when the chela I. has pushed a pellet far away it will do 

 the same with some other pellets before the animal returns in 

 the hole, as if the crab wanted to mend its former inaccurate 

 work. The more sand is carried out the farther the crab rolls 

 the pellet; sometimes it is deposited at the opposite side of the 

 jar. The large chela, as mentioned, is used only from time to 

 time; it does a rough work. In most cases it would only disturb 

 the rolling of the pellets. Therefore it is always raised high in 

 the air in the moment when the side 1-4 presents the pellet to 

 the side 1 1. -IV. 



There is still the problem of locomotion to be solved. As 

 known, during the sidewalk of crabs the legs .directed forward 

 the body while the opposite legs push it. As the digging 



