3^ Papers from the Marine Biological Laboratory at Tortugas. 



crabs formed an association between contact with the glass dish and the 

 presence of water. 



In conclusion it may be said that Ocypoda, like the Crustacea investi- 

 gated by other workers, has memory, is able to profit by experience, and can 

 form habits. 



SUMMARY. 



Adult ocypodas build two kinds of burrows. One consists of a single 

 tunnel extending down in the sand for 3 to 4 feet. The other is similar, 

 except that it is shorter and has a passage branching off from it, which is 

 used for escape. 



Young ocypodas make short burrows, only a few inches long, which 

 often extend vertically downward. 



Breeding in the region of Loggerhead Key probably occurs in the spring 

 and early summer. 



Ocypoda is a scavenger and a cannibal. The eyes do not seem to play an 

 important role in the detection of food, but they undoubtedly lead indi- 

 viduals to objects which may be food. 



That Ocypoda is stimulated by odors was not conclusively shown, but 

 certain experiments point .strongly in that direction. 



The eyes are highly developed, so far as crustacean eyes are concerned; 

 they are quite sensitive to large differences in the intensity of light ; 

 they do not react to different colors ; they aid much in the search for food, 

 in the detection of enemies, and in the accuracy of locomotion. Ocy- 

 podas probably do not have vision such as that of the human eye, nor do 

 they see the color and finer characters of the surface of an object, but they 

 undoubtedly see its outlines and possibly some of the more evident irregu- 

 larities of the surface made evident by differences in lighting. 



The color-pattern seen through the carapace of Ocypoda changes in in- 

 tensity under different conditions of temperaure and light. 



In the absence of light when the temperature is anywhere between 22 

 C. and 45 C, and undoubtedly when it is even lower or higher, a light 

 coloration occurs. 



Generally in diffuse light and even direct sunlight a dark coloration ap- 

 pears, provided the temperature is not too high. 



Usually at low temperatures, not above 35 C, a dark coloration occurs, 

 provided the eye is stimulated by light. 



At high temperatures, above 35 C, a light coloration is the rule, and it 

 occurs independently of the intensity of light. 



No indication of audition was observed in Ocypoda. The so-called 

 " auditory organs " are equilibrating organs. 



Ocypoda has a stridulating ridge on the palm of its large chela. .\ny 

 sound which it may make is probably not heard by other individuals, but 



