Spaulding, Association in Hermit Crabs. 59 



hind the inserted screen first, and feeding in the Hght. From 

 the data already obtained it would be expected that in this a 

 greater per cent, of crabs would from the start make their exit 

 than had in the first experiment made their entrance. This 

 proved to be the case as the following record shows : 



Comparison of this with Experiment I shows that not until 

 the 5th. day was as high a ratio approximately obtained. In 

 both cases of course the crabs are guided by taste ; the two ex- 

 periments together, therefore, serve to demonstrate the natural 

 preference for the light, and the quicker results obtained when 

 this works with than when against the feeding instinct. 



EXPERIMENT IV. 



Lot 3. This same preference was demonstrated by a sec- 

 ond control experiment. Twenty-four crabs were placed in a 

 large rectangular aquarium directly next to a window with a 

 northeast exposure. Half of the aquarium was darkened by 

 holding down with a stone a box with one end taken out. Sand 

 was placed over the entire bottom. 



Twenty observations failed to discover a single crab inside 

 the "dark line" from edge to edge of the box. The crabs, 

 therefore, seem to prefer the light to the darkness, at least in 

 the aquarium. 



EXPERIMENT V. 



Lot 6. A third very similar control experiment was also 

 confirmatory. Thirty crabs, the aquarium jar and screen ex- 

 actly as in Experiment I were employed. The question might 

 arise, would not the crabs possibly "learn" to go behind the 

 screen when this was inserted even though no fish was there, 

 the necessary feeding being done at other times. Should they 

 do this the conclusions from Experiment I would be quite 



