342 BULLETIN OF THE BUREAU OF FISHERIES. 



a century ago, there has been practically no work done on shore and shallow water forms 

 in the region to the south of Beaufort. Of the species reported farther south the great 

 majority are floating forms. 



In the second place, what little evidence there is goes to sustain the conclusion that 

 many of the hydroids have been distributed from a circumpolar area, southward along 

 meridional lines. When out of 51 species collected as far southward as Beaufort there 

 are included as many as 12 species that have been found on the west coast of Europe 

 and also on the west coast of North America, it seems scarcely possible to come to any 

 other conclusion. It might be said that the 17 species reported from Africa would 

 indicate a transference to North America by the Equatorial Current, and that certainly 

 must have a great influence, but when it is noted that 10 out of the 17 are European 

 forms as well, it may readily be, and probably is, the case that these 10 were carried 

 southward in both cases and have direct connection only through the Arctic Regions, 

 while the other 7, being tropical forms, were carried across the ocean by the Equatorial 

 Current, and carried northward with the Gulf Stream. It would seem that the Equatorial 

 Current and its related currents must account for a connection with far-off Australia, 

 as 5 out of the 10 forms are tropical or subtropical floating forms that have been reported 

 along the paths of these currents. On the other hand, the 6 species reported by Hartlaub 

 from the South American coast include none of these forms. None would likely be 

 carried either way across the Equator against the currents, and none could go otherwise 

 unless the Equatorial Current should distribute them both to the north and to the south. 



In the third place, there is a further indication as to the way in which the Bermudas 

 are populated. The Gulf Stream flows northward between Beaufort and the Bermudas. 

 Of the 1 1 species common to the two places, only 2 are of general distribution. The other 

 9 are all forms that would likely be carried on the sargassum with the Gulf Stream. As 

 only 19 species were reported by Congdon, evidently nearly 50 per cent have been carried 

 there from the south by the Gulf Stream. A more detailed survey of each field would 

 naturally indicate a much higher percentage. On the other hand, there is little evidence 

 to show that any of them have been carried directly across, in either direction. 



Finally, it adds to the evidence, if further evidence was needed, that there is no 

 limit to the distribution of hydroid forms. When, by hydroid distribution, Beaufort, 

 in low latitude, is connected with such distant places as Australia, Chile, Bering Sea, 

 and the White Sea, all in high latitudes, not by one but by several species, nothing 

 further need be said. 



The accompanying table puts these comparisons in a more concrete form, especially 

 for the individual species. It is not intended to be exhaustive by any means. It is 

 merely a specific way of stating the comparisons made above. 



