PLANKTONIC STUDIES. 627 



on the trip, Eicliard Greeff, has described the Canary animal streams 

 so vividly that I will here give his description verbatim : 



Our gaze was directed to the highly peculiar long and narrovs' currents, which 

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

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

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

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

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

 absent; to-day they appear 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 single 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 api^earauce. They 

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

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

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

 certain independence. 



If one conies 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 tornloose 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 accumulation of animals, but that the latter voluntarily seek out these smooth, 

 quiet streams, perhaps in (Connection with certain vital -expressions. A trip ujion 

 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 iusjiect them in their unique 

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

 unbroken layer of animals 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 changeableness 

 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 fishermen of Arrecife under the name Za'ni (18, p. 307). 



Although the zoocurrents seem to occur in the most diverse parts of 

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

 recent investigation of them is wanting. What I know al)out them 

 from my own exi)erience and from the contributions of others is 

 essentially the following: 



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

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

 straits between islands or along indented coasts. They are dependent 

 upon the weatlier, especially the wind, and appear as a rule only dur- 

 ing calms. Although in the case of the neritic zoiJcurrents the local 

 course is more or less constant, still it is subject 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 



