الفهرس 
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Abstract
1- A preliminary investigation of the phyto- and the zooplankton of the Nile and the University pond was performed.
The main genera of the plankton were identified.
2- The feeding habits of Synodontis Schall was studied through the macro and Microexamination of the contents of stomachs of young and adult specimens during different seasons.
Specimens from different localities were also investigated in order to study the variation of feeding habits due to different localities.
The digestibility of the different food items was determined by investigating the contents of the rectal contents of different specimens.
It is concluded that Synodontis schall is an omnivorous fish; it feeds on both animal and plant organisms and also on organic debris.
It appears in some cases as a surface feeder depending on planktonic organisms.
In other cases it shows to be a bottom feeder eating mud, organic debris and chironomid larvae.
The relative length of gut was determined and was frond to be 2.6.
3- The gross anatomy and the histology of the digestive system was studied by the dissection of adult specimens and the examination of prepared sections from the respective organs.
Two points of interest emerged from such a study.
The first is the presence of the so called club giant cells in the mucosa of the fore gut.
The second is the diffused nature of the pancreatic islet and acini tissue in the omenta and the invasion of the acini tissue to the liver forming a hepatopancreas.
4- The investigation of the gross and fine structure of the gonads shows that they undergo cyclical changes in different seasons of the year.
During the breeding season the gonads are enlarged in size and contain mature gametes.
On the other hand, after spawning the gonads decrease in size and contain different develop- mental stages of the gametes.
The testis shows that it is composed of lobules of convoluted seminiferous tubules that contain sper- matocytes and spermatids.
The lumen of the tubules contains spermatozoa during the breeding season.
A mearge amount of interstitial cells is observed between the tubules.
Seminal vesicle; the wall of each lobules is composed of one layer of columnar secretary epithelial cells.
The ovary is composed of lobules which contain varying numbers of primary oecytes of different sizes.
The size variation is due to the amount yolk granules accumulated in the cytoplasm of the oocyte.
5- The fecundity of Bagrus docmac was determined according to Stones method by examining 56 ripe females.
The fecundity ranges between 27690- 579236 ova per ovaries.
It was found that the fecundity is correlated in general with the length and weight of the fish.
The average diameter of the ova varies from 0.4 to 1.75. Mm.