120 The Philippine Journal of Science wis 



some of the smaller patches suddenly become animated and crawl 

 away. Another surprise is in store for him when he picks up 

 one of these small patches and finds it to be the cover of a crab 

 carefully hollowed out so as to fit the outline of the carapace, and 

 lightly held in place by the last pair of legs whose dactyli are 

 hooked into the inturned rim (fig. 1). 



Zoologists are familiar with the fact that Cryptodromia 

 tuberculata generally carries a cover of some sort, usually a 

 sponge, occasionally a piece of ascidian, or even rarely a leaf, 

 but so far as I have been able to determine from the literature 

 at hand the activities of the crab while obtaining its covering 

 have not been described. The occurrence of large areas of the 

 sponge encrusting the underside of the rock which sheltered 

 the cryptodromia suggested the possibility of bringing the rock 



Fig. 1. Cryptodromia tuhercvlata Stimpson and its cover. 



with the crabs and sheets of sponge intact into the laboratory 

 and there observing the behavior in an aquarium. This was 

 done, and at the same time the crabs were deprived of their 

 covers. After being left undisturbed for about half an hour,, 

 it was found that several individuals had decorated themselves 

 with new pieces of sponge which though irregular in outline 

 were used as covers and held over the carapace by means of the 

 last pair of legs. 



In order to observe the details of the process of obtaining these 

 new covers, a rock encrusted with a sheet of sponge was placed 

 in a large glass dish of sea water so that the sheet of sponge 

 was on the upper side of the rock. A naked cryptodromia which 

 was placed in the middle of the patch of sponge soon moved 

 toward the periphery. Here it settled down with the abdomen 

 near the edge and the head facing the area of sponge. Then 

 with the chelipeds it began to excavate a groove destined to cut 



