Scope and limitations of this book I am trying here to present the natural history of a land largely created and dominated by two great rivers, the Euphrates and Tigris. All rivers have two main functions, quite different from lakes; they transport water and eroded material sometimes over large distances. The astute Greeks, who penetrated here in the 4th century B.C., called the land Mesopotamia, an apt name; it is the only region in the Near East, except Egypt, having the benefit of large rivers. Another name coined in antiquity was 'Fertile Crescent', stretching from Egypt to present day...

357 Temperature ...358 Transparency and light penetration. 360 Salinity and conductivity 363 Major ions ...365 Dissolved gases and pH 371 Plant nutrients. 375 References 381 27. Phytoplankton: cOlDposition, developlDent and p- ductivity by]. F. TaIling. 385 Introduction...385 Regional Development 385 The headwater lakes 385 a. Lake Victoria . 385 b. Lake Kioga . 387 c. Lake Albert. . 388 d. Lake Tana . . 390 The Sudan plain . 390 The Main Nile in Nubia and Egypt. 395 Limiting factors ...396 Rates of photosynthetic production 397 References ...400 VI. Epilogue by ]. Rzoska 403 Authors Index ....