126 Prof. M'lntosli on the 



of the marine Crustaceans from north to south and east to 

 west. " Land-crabs and river-crabs are chieflj confined to 

 warm climates. Again, very few crabs occur at either end of 

 the globe, but that does not prevent the discovery of _ many 

 crabs living in deep and therefore very cold water in the 

 intermediate zones. There is, besides, a sort of zonal facies^ 

 which an expert in each group would probably recognize. 

 There are circumpolar Amphipods, Isopods, and Sympods 

 (Cumacea), which one would regard with great suspicion if 

 it was said they had been collected at the tropics. But, never- 

 theless, the deep-water communication accounts for the closest 

 family connection between members of the Lithodidc« found 

 far north and far south." {Stehhing.) The same author is of 

 opinion that in some cases there may be isolation and 

 restricted distribution, these seldom going beyond specific 

 distinction. Yet as regards the Crustacea it is difficult to 

 make regional areas of demarcation in the ocean. It would 

 also be difficult to say that any family of marine crustaceans 

 is exclusively tropical and another as exclusively Arctic, and 

 though certain forms are found in deep water {e.g. the Japanese 

 Thauniatocheles), yet representatives of the same family may 

 occur in shallow water. 



In dealing with the families of the marine Polychseta it 

 is also impracticable to map out the ocean in regions to 

 suit their distribution, for almost every family has repre- 

 sentatives in diverse regions ; and although of some it may 

 be said that they are more prominent in tropical or sub- 

 tropical waters, yet other representatives range to the poles. 



As examjjles of families usually considered characteristic 

 of the warmer parts of the sea are the EuphrosynidjB and 

 Amphinomidge, yet examples of both occur in Norway and of 

 the former in Greenland ; indeed their range is almost 

 cosmopolitan. The Eunicidae likewise are often conspicuous 

 in tropical and subtropical seas, yet the abundance and size 

 of some from the shores of Norway and from the North 

 Atlantic show the cosmopolitan distribution of the group. 

 With our present knowletlge it can hardly be said of any 

 family that it is, on the one hand, a purely northern or a 

 purely southern, or, on the other hand, a purely temperate 

 or a purely tropical one. Some Annelids range from Green- 

 land to Japan, from Norway to the Cape and New Zealand, 

 and many are cosmopolitan. 



In considering how it has happened that the same form is 

 found in Greenland, Europe, and Japan, some, like Sir John 

 Murray, would suppose that such had been universally dis- 



