Habits of the Crab 205 



ON THE HABITS OF THE CRAB DOTILLA 



FENESTRATA, HILGENDORF, WITH SPECIAL 



REFERENCE TO THE MODE OF FEEDINa 



By R. BiGALKF., M.A. 



At low water a portion of the sandy beach at Polana, 

 Louren^o Marques, may be seen to be strewed with what appear 

 to be grains of gravel, but closer examination shows that these are 

 really .small balls of wet sand varying in size up to about Yq of 

 an inch in diameter. A large number of apertures are also to jo. 

 seen scattered among the globules of sand; these apertures vary in 

 diameter from less than ]/4 of an inch to about Yz oi an inch, ac- 

 cording to the size of the crab inhabiting the burrow. 



If the observer remains perfectly still for a few minutes he wiii 

 see a small crab pop out of each burrow and withdraw again im- 

 mediately. After repeating this a few times, and having over- 

 come its fright, there emerges from each burrow a small crab, and 

 in casting one's eyes around many hundreds of such little creatures 

 will be seen. The body of the largest of them measures about 

 1 1 mms. in greatest width and 1 mms. in greatest length. The 

 crabs are found in what may be termed a zone of sand situated 

 closer to the high water than to the low water mark, but this zone 

 is almost level, and the sand remains very wet from the time it be- 

 comes uncovered until the tide again returns. 



In order to observe the little creatures it is essential to remain 

 quite still, for they are very wary and at the least movement on the 

 part of the observer they disappear into their burrows. They are 

 able to see well since the eyes are situated at the apices of movable 

 stalks about 4 mms. long in the largest of them; these eye-stalk? 

 stand up prominently from the anterior border of the carapace and 

 diverge slightly from one another. At the base of each eye-stalk 

 is a transversely lengthened orbit into which each stalk can be 

 folded down. The stalks are folded dcwn into the orbits when 



