2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 6 1 



rivers, and this is especially true of the Trinidad, are extensive 

 swamps. The Chagres is a swift flowing' stream, sometimes torrential 

 in character, and does not furnish a suitable environment for any 

 extensive development of plankton organisms. The swamps form a 

 suitable environment for plankton, but, connected together as they 

 are, would not lead one .to expect any great variety. 



The Gatun Lake will eventually be a large body of water with a 

 surface of 164 square miles and a depth of 47 feet. At the time the 

 collections were made, the lake was very small. Especially careful 

 collections were made in this lake and in the neighboring waters and 

 in sufficient numbers to give a good idea of its flora and fauna. 



As has been stated before there are no natural lakes in the Canal 

 Zone. The Canal Commission, however, has built, for sanitary pur- 

 poses, a series of reservoirs and these, having been in existence for 

 a considerable period, may be considered as lakes. Following is a 

 list of these reservoirs with the dates of their construction. These 

 dates are stated as given by Downes (Downes, 1910, 1). The depths 

 given are the maximum depths at the .time the collections were made. 



Built Elevation Depth 



Cocoli 1909 36 feet 33 feet 



Rio Grande 1906 240 " 50 " 



Camacho 1907 370 ' 45 ' 



Carabali 1906 76 " 10 " 



Agua Clara 1910 68 " 30 " 



Brazos Brook 1906 48 ' 25 ' 



While the Rio Grande is considered as constructed in 1906, it is 

 really an old French reservoir which was built sometime between 

 1882 and 1889 and has had a continuous existence since that time; 

 it covers an area of 72.7*] acres. 



Besides these reservoirs there is the Mindi reservoir in .the neigh- 

 borhood of the Brazos Brook reservoir which was to be abandoned 

 soon after the collections were made, and, at that time, no attempt 

 was made to keep it in sanitary condition. 



There is a reservoir at Toro Point but this, when visited, was found 

 dry. These reservoirs were made by constructing dams in places 

 where the waters of small streams could be impounded. The beds 

 were cleared of vegetation except in the case of the Cocoli, and after 

 construction, the shores were kept clear of vegetation to a distance of 

 fifty or more feet from the margin. The condition of the waters in 

 these reservoirs has been explained in detail by Downes (Downes, 

 1910). The reservoirs were all "plankton-poor." This is what 



