VIII, D, 2 Coivles: Habits of Tropical Crustacea 121 



off a small piece from the sheet of sponge. After the piece had 

 been isolated, the crab lifted the edge, pushed itself under, and 

 finally dislodged the piece from the rock. The cryptodromia then 

 caught hold of this new but ragged cover by means of its last 

 pair of legs and carried it off. Four stages in this process are 

 shown on Plate I. In the upper left hand comer of fig. 1 the 

 crab is seen rather indistinctly cutting out the piece, in a similar 

 region of fig. 2 the cutting is completed, in fig. 3 the crab has 

 pushed its way under the newly separated piece of sponge, and 

 finally in fig. 4 the piece is being carried off. All of the figures 

 are of further interest in that they show at the right hand edge 

 a little below the middle another cryptodromia whose original 

 cover has not been tampered with. In addition to the sheet of 

 gray sponge which may be seen in all the figures, there are 

 also many patches of an ascidian (light in color both in nature 

 and in the figure) which are sometimes used for covers. 



The method of obtaining covers which I have described is 

 undoubtedly the same as the one used by Cryptodromia tuber- 

 culata when living under natural conditions, for I have found 

 individuals under rocks with similar unfinished covers which 

 undoubtedly had been recently cut from sheets of the sponge. 

 It is of interest to know that the new ragged covers cut out 

 by the crabs in the laboratory began to assume a more regular 

 appearance after a few days and to take on the shape of the 

 covers found on the cryptodromia when living in the sea. 



TUBE BUILDING OF ALPHEUS PACHYCHIRUS 



It is well known by zoologists that one of the "pistol crabs," 

 Alpheus pachychirus Stimpson, lives in a tube which it con- 

 structs of the matted thread of a filamentous alga. Richters 

 (1880)1 and de Man (1888) ^ published this information, but 

 Coutiere (1899)^ has not found the same species living in alga- 

 tubes at Djibouti. So far as I have been able to ascertain with- 

 out having access to the paper of de Man, the behavior of this 

 crustacean while constructing the alga-tube has not been de- 

 scribed, so the following notes may be of interest. 



On the underside of the rocks in the littoral zone of Port 

 Galera Bay there may be found the sac-like alga-tubes of Alpheus 



'Beitrage zur Meeresfauna der Insel Mauritius und der Seychellen. 

 Berlin (1880), 164. 



^Arch. f. Naturg. (1888), 5. 



' Theses presentees a la Faculte des Sciences de Paris : Les "Alpheidae," 

 morphologic externa et interne, formes larvaires, bionomie. Paris (1899), 

 500. 



