94 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



colours. Moreover, individuals can to a considerable 

 extent change their colour when the environment is 

 altered. The first Port Erin Annual Report (1893) con- 

 tained a short account of this animal, with a plate showing 

 the chief colour variations. Since then Messrs. Gamble- 

 and Keeble have made a number of interesting experi- 

 ments, and have shown that at night the colour of all 

 varieties is a deep blue. 



The Decapoda or higher Crustacea may be divided 

 into 3 sets : — 



(1) Those that have the tail part or abdomen stretched 



out behind the carapace or shield that covers the 

 head and thorax, as in lobsters, shrimps and 

 prawns (Macrura). 



(2) Those where the abdomen is smaller and is folded 



up underneath the carapace, as in crabs 

 (Brachyura). 



(3) Those where the abdomen is neither completely 



stretched out nor folded up, and is often 

 anomalous in shape (Anomura). 



Figure XV. shows Macrura, fig. XVII. Brachyura, and 

 fig. XVI. two interesting kinds of Anomura, which we 

 generally have on view in the Aquarium. Xo. 2 is 

 Galathea squamifera, the ' k squat-lobster," of which one 

 kind, of a blackish colour, is frequently found under 

 stones at low tide in Port Erin Bay, while another bright 

 red kind is obtained from deeper water by dredging. The 

 abdomen, it will be seen, is partially turned under the 

 body, but can be extended and flapped up and down when 

 swimming. The other figure (1 in fig. XVI.) shows a 

 " hermit crab " (Eupagurus frideauxii), with its 

 anomalous abdomen tucked into an old Molluscan spiral 

 shell, on the outside of which is a special kind of sea- 



