7 2 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 60 



established his headquarters at Empire, and remained in the field 

 until February 16. 



The topography of the Zone is such that it is not a particularly 

 good collecting ground for plankton. The region visited is practi- 

 cally destitute of lakes, there are but few permanent pools, and 

 although the lowlands of the Atlantic slopes form a huge swamp, 

 the waters in this locality are so connected that no great variety of 

 forms is found. The south slope is abrupt, with no permanent bodies 

 of water, and the streams are small and more or less temporary. 



Fig. 79. — Rio Grande Reservoir, Canal Zone, showing workmen clearing 

 the shores to prevent decaying vegetation from falling into the water. 

 This is an old reservoir dating from the time of the French occupation. 

 Photograph by Marsh. 



Especial attention was paid to the old reservoirs which form 

 little lakes, and ordinarily would contain some of the typical flora 

 and fauna of the immediate region, but these bodies of water are 

 " plankton poor," as compared with similar bodies in a temperate 

 climate; for, inasmuch as the temperature of the air is practically 

 uniform throughout the year, there is no vertical circulation of the 

 water, except where it is shallow enough to be affected by the winds. 

 The conditions at the bottom of the deeper waters of the reservoirs 

 are such as to make life impossible. Careful collections were made 



