THE INSURGENCE OF LIFE 



157 



FIG. 37. Cross section through a land-crab (Birgus latro). (After 

 Semper.) 1. The over-lap of the cephalothorax shield. 2. The respir- 

 atory tufts. 3. Two small gills. 4. The base of a leg. 5. The ventral 

 nerve-cord. 6. The food-canal. 7. The pericardium around the 

 heart- 



ened and scuttle off backwards, propelling themselves with 

 their long anterior legs in a series of ungainly jerks. They 

 seem quite conscious of the comparative defencelessness 

 of the abdomen, which they endeavour to thrust under 

 logs or into holes among the roots of trees. But they 

 never carry any protective covering. Their dietary must 

 also have changed greatly, for they eat fruits of various 

 kinds (such as sago-palm and screw-pine) and carrion of 

 all sorts. As their name suggests, they are incorrigible 

 thieves, stealing from the camp not only what is or 

 even looks edible, but apparently anything that has been 

 handled, cooking utensils, bottles, and clothes. Dr. 

 Andrews complains that he had a geological hammer 

 practically ruined by having its handle splintered in the 

 powerful claws of one of the robbers ! 



The case of the land-crab suggests another good instance 

 of adaptation to change of habit. It is to be found in a 

 Philippine crustacean, Thalassina anomala, which is in 

 some respects like a link between the long-tailed prawn 

 type and the hermit-crab type. It is a common burrower 



