CH. Ill] RANGE OF ARCTURUS. 125 



Distribution of Crustacean Arcturus as illustrative 

 of connection between range and temperature. 



It is chiefly marine organisms which show a close 

 interdependence of temperature and distribution. The 

 Isopod genus Arcturus and the nearly related Astacilla 

 prevail chiefly in the antarctic hemisphere; it is only 

 recently however that they have been obtained from that 

 part of the world. Until the voyages of the German ship 

 " Gazelle " and the English vessel " Challenger " the two 

 genera were only known from the northern hemisphere. 

 Four or five species of Astacilla occur on the coasts of 

 Great Britain, N. America and Northern Europe; while 

 the large Arcturus baffini is the only representative of its 

 genus from the north, which is an inhabitant of shallow 

 seas. It is in the antarctic region of the globe that 

 Arcturus is so prevalent. Two species named Arcturus 

 coppingeri and A. americanus occur in the shallow water 

 off the coasts of Patagonia ; three species of Arcturus, viz. 

 A. furcatus, A. studeri, A. stebbingi, are met with on the 

 shores of Kerguelen, besides a peculiar genus still refer- 

 able to the same family and containing one species 

 Arcturides cornutus. A single Astacilla, A. marionensis 

 lives, as its specific name implies, on the shores of Marion 

 Island, not so far from Kerguelen; finally there is a 

 peculiar form with eyes on long but immobile stalks, 

 Arcturus o&ulatus, on the shores of South Australia. In 

 addition to these inhabitants of shallow water there 

 are a number of species which are only found in deep 

 water and one {Arcturus furcatus) which lives in both 



