xv > 1 Cowles: Habits of Tropical Crustacea 87 



I have observed other hermit crabs of the species Pagurus de- 

 formis which were even more inaccurate in their actions than 

 the one we have just considered. In one case a hermit changed 

 to an empty shell, worked on the anemones of the old shell for a 

 few moments, and then took up its habitation again in the old 

 shell. Soon, however, it inserted its abdomen again into the new 

 shell and after about an hour's work succeeded in loosening an 

 anemone. This it lifted upside down to the upper surface in 

 such a manner that it became attached to the apex of the shell 

 merely by one edge of the base where it hung with the tentacles 

 hanging downward. Soon, however, partly as the result of the 

 hermit moving about and turning its shell, the anemone became 

 firmly attached in its normal position with the tentacles directed 

 upward. About an hour later the hermit succeeded in removing 

 another large anemone from its old shell, but instead of setting 

 it on top the hermit placed it in the mouth of the new shell where 

 the smaller species of anemone is usually put. The transfer of 

 the latter (there were two of these) was not seen. Observations 

 on this hermit were discontinued until the next morning when 

 I found that both of the large anemones were in their usual po- 

 sitions on the back of the new shell, the one formerly placed at 

 the mouth either having been transplanted by the hermit during 

 the night or having moved of its own accord to the outside of the 

 shell. One of the small anemones had been removed from the 

 old habitation and apparently an attempt had been made to 

 attach it at the mouth of the shell; but the transfer had been 

 inaccurate, so that the anemone had become attached at the base 

 of the walking legs of the crab near the mouth. The other 

 small anemone was still attached to the old shell. 



In the case of the species of hermit crab Pagurus asper the 

 transfer of anemones from one shell to another was accomplished 

 in practically the same manner as in the case of Pagurus defor- 

 mis, except that the movements were slower. 



My observations on the active and speedy shore crab Ocypoda 

 arenaria Catesby 1S and the experiments of Yerkes and Huggins 1+ 

 with the crayfish show that, in the case of the former, past ex- 

 periences leave an impress at least on the nervous system, and 

 that the crayfish is able to solve very simple problems, such as 



"Cowles, R. P., Habits, reactions, and associations in Ocypoda arena- 

 ria, Papers Tortugas Lab. Carnegie Inst. Washington 2 (1908) 34. 



"Yerkes, R. M., and Huggins, G. E., Habit formation in the crawfish 

 Cambarus affinis, Harvard Psychological Studies 1 (1903) 565. 



