GEOGRAPHICAL DISTRIBUTION. 221 



The mode of branching of the canals agrees closely with that described 

 for P. ornata, the resemblance to McCrady's figure being extremely close, 

 and it is the same as has been described by Maas (: 05). Each of the 

 four radial canals bifurcates about one-fourth of the distance from its 

 origin to the margin. This condition, with eight tentacles opposite the 

 eight canals, is seen in specimens in which gonads have not yet appeared. 

 The eight canals thus formed branch then again, the second bifurcation being 

 the locality where stolons occur in the specimens described by Maas (: 05). 

 This is the normal limit to the branching in the Atlantic P. ornata. But in 

 P. ornata var. stolonifera most of the larger specimens have the canals still 

 further subdivided, in the manner shown diagrammatically (PL 41, fig. 7). 

 This is a very different type of branching from that exhibited by P. flavi- 

 cirrata Brandt, from the northwest coast of North America, in which each 

 radial canal branches once dichotomously, each of the two resulting canals 

 sending off numerous lateral branches from one side only (Brandt, '38 ; A. 

 Agassiz, '65). 



Color. — In life the gonads and tentacle bases are usually pale green ; other 

 portions are colorless ; some specimens however are entirely without color. 



Prohoscydactyla ornata has been recorded only from the Atlantic coast of 

 North America, where its range is known to extend from the West Indies 

 to Cape Cod. The variety stolonifera was described by Maas from the 

 Malaysian region, and Huxley's specimen was taken in the Louisiade Archi- 

 pelago. Together with the present captures these records show that it is 

 very generally distributed over the Tropical Pacific. In the colder regions 

 of the north Pacific its place is taken by the much larger P. flavwirrata. 



Geographical Distribution. 



The oceanic region traversed by the " Albatross " in 1904-05 is of great 

 interest to the student of zoogeography, for two reasons. In the first 

 place, it is bounded on one side by the great Humboldt, or Chili-Peruvian, 

 Current; a current of much lower temperature than the adjacent regions, 

 and comparable in size, in volume, and in regularity of flow to the Gulf 

 Stream, to the Guinea, the Benguela, or to the Japanese Current. In the 

 second place, it is one of the largest uninterrupted oceanic areas on the 

 globe, so that here, if anywhere, we might expect to find the pelagic fauna 

 unaffected by the disturbing elements, such as vertical circulation of water, 



