VIII. D, 2 Coivles: Habits of Tropical Crustacea 123 



edges of the mat thus apposed (fig. 3). The slender chelate 

 leg of one side was thrust through the edge of the mat of the 

 corresponding side and then bent over until the open chela was 

 able to take hold of a thread of alga near the edge of the opposite 

 side. The leg was then drawn back, pulling with it the thread 

 which, however, still remained entangled in the opposite side, 

 thus making a simple stitch. At the same time that the opera- 

 tion just described was taking place, a similar one was per- 

 formed by the other slender chelate leg, the result being that 

 from each side a thread was drawn out part way and pulled 

 through the opposite side. In this manner the edges of the 

 furrow were gradually fastened and a tube formed. The alpheus 

 did not sew up the tube from one end to the other without a 

 break, but stitched it together at intervals first and later closed 

 up the spaces between. The movement of the slender chelate 

 legs was very rapid so that after ten minutes a tube about 10 





Fig. 3. A diagrammatic view of Alpheiis pachychirtis Stimpson sewing the edges of 



an alga-mat together. 



centimeters long had been formed. At the end of this time, 

 as the result of some signal from the male or simply by chance, 

 the female, which had been resting quietly several centimeters 

 away, backed into the new tube with the male. 



Having seen the method of making a tube out of a continuous 

 sheet of alga, I was anxious to determine if the alpheus could 

 construct a new tube out of the fragments of an old one. A 

 tube was opened and torn into such minute shreds that a large 

 number of single filaments separated out. A pair of alpheus 

 was placed in a dish of sea water where they soon retreated 

 under a more or less flat stone so arranged that there was a 

 space below it. The mass of individual filaments and small 

 fragments of the alga were then placed in the dish. After about 

 five minutes, one of the crustaceans began to draw the alga 

 under the stone, and fifteen minutes later, on siphoning the water 

 out of the dish in order to add more water, it was found that the 

 filaments and the fragments had been so securely attached in 

 several places to the underside of the rock that they remained 



