PLANKTONIC STUDIES. 627 



ou the trip, Eictiard Greeff, hats desciibed the Canary auiuial streams 

 so vividly that I will here give his description verbatim: 



Our gfaze was directed to the highly ]>eciiliar long and narrow currents, which 

 are of very especial importance for pelagic lishery with fine nets. If one looks at 

 the calm sea, especially from an elevation over a wide expanse of water, here and 

 there are seen strongly marked shining streaks, which intersect the snvfacc as long 

 narrow bands. Their course and place of appearance seem to bo continually chang- 

 ing and irregular. Sometimes they are numerous, sometimes only few or entirely 

 absent; to-day they apjiear here, to-morrow there; some have one direction, others 

 the opposite or crossing the first. Occasionally they run along close to one another 

 and unite in a swingle stream. If one approaches this streak it becomes evident 

 that here in fact a current prevails different from the movements of the surrounding 

 water, and that thereby is brought about the smooth band-like appearance. They 

 give the impression of streams cutting through the rest of the ocean, Avith their own 

 channel and banks, which, notwithstanding the great variations in the time and 

 place of their appearance, yet during their existence, wliich is often brief, show a 

 certain independence. 



If one comes upon such streams, which are not too far distant from the coast, he 

 sees that all the smaller, lighter objects which formerly scattered over the surface, 

 floated about or cast upon the shore, were drawn into it. Pieces of wood and cork, 

 straw, alga-, and tangle torn loose from the bottom, all in motley procession are carried 

 along in this current. But in addition (and this is for us the most important 

 phenomenon) all the animals belonging in the region of these currents arc drawn in 

 and fill it, often in such great quantities that one is tempted to believe it is not 

 merely the mechanical influence of the narrow stream which has brought about such 

 an accunmlation of animals, but that the latter voluntarily seek out these smooth, 

 quiet streams, perhaps in connection with certain vital expressions. A trip upon 

 such a pelagic animal road furnishes a fund of very interesting observations. We 

 can lean over the edge of the boat and review the countless brightly colored sea- 

 dwellers, sometimes passing by singly, so that we can inspect them in their unique 

 peculiarities, sometimes in such thickly massed hordes that they seem to form an 

 unbroken layer of animate for a few feet below the surface. Yet these animal roads, 

 where one meets them in the sea, will always form the most certain and richest 

 mine for the so-called pelagic fauna, although naturally, from their changeablenese 

 and their dependence upon a calm sea, they can never be definitely counted upon. 

 Likewise, the origin of these noticeable streams and their significance in the natural 

 history of the sea is still almost completely dark, in spite of the fact that they can 

 be observed in almost all seas and under favorable circumstances daily, and also are 

 known to the fisliermen of Arrecife under the name Zain (18, p. 307). 



Althongh the zooourrents seem to occnr in the most diverse parts of 

 the ocean, and have often aronsed the astonishment of observers, yet a 

 recent investigation of them is wanting. What I know about them 

 from my own experience and froni the contributions of otliers is 

 essentially the following: 



The zoocurrents occur in the open ocean as well as in the coast 

 regions, particularly in the region of those nerocurroits which run in 

 straits between islands or along indented coasts. They are dependent 

 upon the weather, especially the wind, and ai)pear as a rule only dur- 

 ing calms. Although in the (^ase of the neritic zoocurrents the local 

 course is more or less constant, still it is sulyect to daily (or even 

 hourly) variations. Their breadth is usually between 5 and 10 meters, 

 but sometimes 20 to 30 meters or more; their length is sometimes only a 



