124 The Philippine Journal of Science wis 



hanging after the water had been removed. On several occa- 

 sions after refilling the dish the alpheus was seen pushing 

 filaments upward in the attempt to attach them to the rock under 

 which they were building the tube. They were successful in 

 this, every now and then the filaments becoming caught on the 

 sharp edges of the coral rock or entangled in some other kind of 

 alga growing on the rock. After a time the mass of alga which 

 had been drawn under the rock began to take on the shape of 

 a tube as a result of the activity of the slender pair of chelate 

 legs. These legs worked quickly, first here and then there, draw- 

 ing free edges together and stitching them. When the alpheus 

 found a hole in the rapidly forming tube, the slender legs came 

 through, caught hold of the filaments of the alga, and manipu- 

 lated them in much the same manner as a man might the thread 

 with which he darns a hole in his sock; that is, by drawing 

 the edges of the hole together and fastening them. 



The next morning a fairly well-made tube was present in which 

 the outer surface was uniform, the shreds having been worked 

 into an even surface. The cavity was distinct, and the inner 

 walls smooth. This new tube measured 11.5 centimeters in 

 length, about 2.5 centimeters in width, had one opening to the 

 exterior, and harbored the pair of alpheus. 



I 



