14 Pratt, Bipolar Theory. 



Scaltbregvia has not been taken in tropical waters 

 Off New Zealand it has been taken at a depth of 7CK) 

 fathoms, and may therefore be classed as a member ol 

 the subsurface fauna. It is possible that it may pass 

 through the tropics by means of the deep sea, but as it 

 has not been taken at intermediate stations between the 

 north and south extra-tropical waters, we must regard it 

 as a " bipolar" form. 



The controversy on the " Bipolar Theory " has been 

 limited, more or less, to a discussion of the distribution of 

 forms known to occur in deep water. As the littoral 

 marine fauna is supposed to be the most primitive, and 

 therefore the one from which all other faunas are derived, 

 it was thought that an investigation of the distribution 

 of littoral forms would be interesting, in that it would 

 increase the evidence for or against this theory. With 

 this object I have studied the distribution of the Pol)xhaeta 

 from the shores of the Falkland Islands. 



The collection of Polychreta from the Falkland Islands 

 numbered 13 species ; of these : 



One is cosmopolitan : Spirorbis borealis, Daud. 



Fight have been taken in the southern hemisphere : 

 ( Hcrmadion) inagallusnsis, Thclepus spcctabilis, Autolytns 

 simplex, Eteone spathocephala, Sabella ceratodaula, Promenia 

 jucuiida, Platynereis magathcBusis, Sabellaria fnacropalea. 



Four are represented in temperate waters of the 

 northern hemisphere but have not up to the present been 

 taken within the tropics : 



[\.) Goniada norvegica, var. falklandica. 

 Common to Norway and the Falkland Islands. The 

 genus is cosmopolitan in temperate and tropical waters, 

 but has not been taken in very deep water. 



