NOTKS ON Till'; HI II \\TOR OK THK FIDDLMR CRAB. 1X7 



work progresses the crab has to carry its burden from a greater 

 and greater depth. The legs II.-V. are free in pulling the body, 

 but the legs 2-4 are holding the sand. The chief role in the 

 locomotion on the inner side is played by the leg 5 which is 

 never used for burrowing. In the later stages of burrowing the 

 leg 2 also begins to help a little. Its articulations pro-dactylo- 

 podit and mero-carpopodit are moving and pushing the body, 

 while the meropodit holds the pellet. To a certain extent also 

 the small chela helps. Only the legs 3 and 4 remain motionless, 

 holding the sand. 



Another interesting particular. When the burrow is just deep 

 enough to hide the thorax but the legs I.-V. remain outside, the 

 crab often grasps the edge of the hole with legs II.-V. helping 

 to move the body out of the burrow. There is the danger that 

 the edge will break under this effort and the sand will fall into 

 the burrow. Thus the crab grasps the edge at four points 

 possibly distant from one another embracing about 160 of its 

 circumference. In all other cases the legs are held much closer 

 together. 



The burrow is perfectly circular in every transverse section. 

 This becomes possible because the crab changes very often its 

 position within the tube turning around the transversal axis of 

 the body. As the canal of the burrow is oblique the animal 

 sometimes walks along it having its legs directed towards the 

 upper wall and the back touching the lower one. Consequently 

 Uca comes out from the burrow touching different points of the 

 hole and this causes the pellets to be deposited at different spots 

 around it. But the most of them are deposited in the direction 

 which is a prolongation of the inclined burrow. Evidently 

 walking along the lower wall of the canal is easier and occurs 

 oftener. . 



Still repeating all those described movements the animal 

 succeeds in digging a deep burrow ending blindly at the bottom 

 of the jar. However sometimes Uca stops digging before the 

 bottom is reached. As mentioned above the inner end of the 

 burrow forms a kind of chamber markedly larger in diameter as 

 compared with the canal. The animal is especially careful in 

 making it and often it will spend hours in finishing the end- 



