112 A HISTOEY OF RECENT CRUSTACEA 



are. dispersed upon the shore, but that in winter the females 

 collect on the deeper rocky ground in particular spots in a 

 great crowd, and pile themselves up in such numbers that 

 they form a sort of mound, which from the depth of eighty 

 to a hundred feet ascends until the glimmer of it can be 

 seen at the surface of the water, and that then the Istrian 

 fishermen go out with two, four, or six boats, surround this 

 living tower with their nets as easily as possible, and so 

 make a speedy capture. Professor Stalio, in 1877, en- 

 dorses this wonderful tale, except that in his account the 

 boats employed are only two or four, and the instinct which 

 leads these creatures to cling together and climb up one on 

 another's back only produces a great pile of several feet in 

 height. Yet anything much less than Olivi's submarine 

 mountain of crabs would scarcely be visible from the sur- 

 face at the depths which he mentions. 



The Mediterranean possesses another closely allied spe- 

 cies, Maia, verrucosa, Milne-Edwards, smaller in size, and 

 covered with warts or tubercles, instead of spines or prickles. 

 This little crab led the way in quite recent years to some 

 observations that throw a new light upon the mental powers 

 of the Crustacea. 



A great many of the Oxyrrhyncha have at all periods 

 excited the surprise of collectors, when dealing for the 

 first time with living specimens, by their often extreme un- 

 tidiness. They are overgrown with algae and ever so many 

 kinds of sedentary animals. They are undoubtedly them- 

 selves slow-moving creatures, and it was not unnaturally 

 supposed tha.t these colonies with which they were encum- 

 bered and disfigured were at once a proof and a result of 

 their extreme sluggishness. Dr. Graefie had once occasion 

 to carry into the aquarium at Trieste a specimen of Maia 

 verrucosa, which had been stripped of most of its vegetable 

 costume. He happened to place it in the same vessel with 

 a large mass of the polyp known as Dead Man's Fingers. 

 The next day, to his astonishment, he found the whole 

 back of the Spider-crab covered with pieces which had 

 evidently been snicked out of the Alcyonium. To make 

 sure, he kept watch, and at length had the sweet satis- 



