252 THE ZOOLOGIST. 



way can readily be tested by taking bold of the disguising mass 

 and giving it a gentle pull, when a portion of it will usually 

 come away in the fingers, the animal at the same time sidling 

 off in the opposite direction. Indeed, it is often sufficient simply 

 to seize the mass, when the Spider-Crab will itself give a pull 

 in order to get free. It is usually the long outstanding mass on 

 the rostrum which is presented to the enemy as the Spider-Crab 

 retreats with its peculiar sidelong gait. 



The Four-horned Spider-Crab feeds readily upon seaweeds 

 of various kinds. It will eat in the daytime, especially if it is 

 hungry, but it is after nightfall that it prefers to feed. The 

 quantity of seaweed devoured may be measured by the rapid 

 disappearance of the seaweeds in the aquarium and by the masses 

 of faeces daily deposited. .It may here be mentioned that on one 

 occasion, when there was a shortage of seaweed for a few days, 

 two Spider-Crabs which were living in a tank at that time were 

 given some of the common freshwater Canadian weed (Elodea 

 canadensis), which they cut up and ate. Bell mentions that 

 these Spider-Crabs would congregate in vast numbers in the 

 prawn and lobster pots at Bognor, attracted, he thought, by the 

 garbage used as bait ; * but I have never been able to get any of 

 them to eat raw beef, and only occasionally, and reluctantly, to 

 take dead fish. All the individuals studied by me have been 

 females, or males whose claws had not attained their full size ; 

 and it is possible there may be some difference between the 

 habits of the younger and older Spider-Crabs, or between those 

 of the males and females, the adult males being bold enough to 

 approach and feed upon substances likely to attract animals 

 which might attack the Pisa itself, while the younger males and 

 females venture only to take food which can be obtained with 

 less risk. Indeed, Bell remarks t that those found in the pots 

 were much larger and finer than any he had seen elsewhere. I 

 have observed that the masses of seaweed used as a disguise may 

 also serve as a food-reserve if the animal is unable to obtain 

 sufficient to eat. One individual, for example, enveloped itself 

 in a mass of seaweed some four inches in height, and it gradu- 

 ally removed and ate the whole mass in the course of the follow- 

 ing fortnight. Schmidtlein mentions J that he has seen " Pisa- 



* Ibid. p. 24. f Ibid. p. 24. | hoc. cit. p. 23. 



