Field-Labourer^ 69 



the limy mud-flats of the East Indian Archipelago. 

 At present, we believe, their work has been watched 

 only on the Keeling or Coroz Islands ; but what crabs 

 are doing now crabs may have done, and have most 

 probably done, in the past, so that some part at least 

 of the present fertility of other mud-flats, perhaps of 

 coral islands, may be owing to them. 



But what, it may be asked, can crabs do ? They 

 burrow, for one thing ; and they make their homes so 

 close together that as many as a hundred and twenty 

 of these narrow, corkscrew holes have been counted in 

 a space only two feet square, so that the ground is very 

 thoroughly perforated indeed. And they not only 

 burrow, but are incessantly busy carrying down twigs, 

 bits of seaweed, scraps of coco-nut shell, seeds, and so 

 forth, with the object of making themselves comfort- 

 able, it is to be supposed, and yet it almost seems as if 

 they laboured, some of them, in this industrious way 

 simply and solely for the sake of improving the soil. 



One of these crabs works so near the water that its 

 burrows are covered at high tide ; another works a 

 little further in, and a third further still, where the mud 

 is dry ; but what is curious about this last is that as 

 soon as the white, chalky mud has been turned into 

 dark vegetable soil, which it is by the decay of the 

 various things dragged into it at once the crab goes 

 off to another fresh spot, and begins all its work over 

 again. Perhaps it does not like decayed vegetable 

 matter ; but the result is that it is always at work, and 

 must get through a good deal of digging in the course 

 of its life. 



Further inland still, the soil is dry and turned up to 

 the sun and rain by the ' great coco-nut crab,' one of 



