الفهرس 
introduction and review of literatureOnly 14 pages are availabe for public view
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Abstract
Some aspects of the morphology and the biology of Gambusia affinis holbrookii were studied through the investigation of 1491 specimens,
1- A colony of Gambusia affinis holbrookii was established in the University ponds.
2- 200 specimens were reared in aquaria in the laboratory and observations on their breeding were per¬formed.
3~ The morphology of the pectoral and anal fins of the uadifferentiated young and mature males and females was studied in preserved specimens. Their skeletal structures were described through investigation of the alizarin preparations.
4- The development of the skeletal structures of
the anal fin in the male and the female specimens was
studied at different growth stages of the respective
specimens and histograms were drawn to show these relations,
5- Both the pectoral and anal fins of the male show sexual dimorphism. The pectoral fin is slightly modified
while the anal fin is transformed into a transmitting organ, the gonopodium.
6- The feeding habits of the young and matur
specimens were studied through the examination of the intestinal and rectal contents of 823 specimens. The feeding behaviour was also observed on the colony that was established in the University ponds and on those kept in the aquaria in the laboratory,
7- The variation of the feeding habits of the young
and mature specimens during the different seasons was
recorded. The intensity of feeding and the digestability
of the different food items was also studied.
8- A conclusion is drawn that Gambusia aff in is
holbrookii is mainly a plankton feeder. The developmental
stages of the mosquito, Gulex pipiens form one of the main
food items consumed especially during Spring, Summer and
Autumn seasons.
9- The morphology and histology of the digestive
system were studied.
10- The mouth is directed upwards, protrusible and helps surface feeding. Six small buccal and pharyngeal
teeth patches are present. They help in holding and kill¬ing large preys,
11- The stomach is lacking, the oesophagus passes
into the intestinal swelling, through a pyloric valve.
12- The liver occupies the left part of the body
cavity and is composed of two lobes. The choledocal duct
opens at the ventral side of the intestinal swelling close
to the pyloric valve,
13- The pancreas is situated in the hepato-intestinal
omentum, hepato-splenic omentum, ensheathes the blood
vessels of the hepatic portal system and also invades the
liver as the intrahepatic pancreas. The latter is
endocrine in nature, while the former patches consist of
both endocrine and exocrine patches. Furthermore, a compact
large islet tissue, the principal islet is found near the
gall bladder in the hepato-intestinal omenturno
14- The buccal and pharyngeal mucosae are formed of
a squamous epithelium and contain few taste buds and mucus-secreting cells.
15- The oesophageal mucosa contains numerous oval
[and spheroidal mucus-secreting cells. These exist in
Superimposed layers towards the lumen and in the crypts of
the villi. They are situated on the squamous epithelial layer that lines the oesophagus.
16- The muscular coat of the•oesophagus is formed
of circular and longitudinal striated muscle fibres.
17- The muscular coat of the pyloric valve is composed
of circular striated muscle fibres.
18- The intestinal mucosa is composed of simple
columnar epithelial cells among which numerous goblet
cells are found. There is no muscularis mucosa in the
intestine. » Granular eosinophilic cells are numerous in
the submucous layer.
19- The breeding habits of the naturally living and
aquaria reared specimens were studied. It was found that
in ponds and in aquaria mature females begin to give birth
to their first brood of young during the last week of March,
Successive broods are then given each month. The last
brood in aquaria reared specimens was born during the last
week of November while the last brood observed in the
University ponds was given during the last week of August,
The ovaries of specimens from the ponds were found to be
in the resting stage during winter.
20- The fecundity was studied through counting counting the number of developing embryos in the ovaries of 1277 females.
It was found that fecundity is directly proportional to the size of the specimens.
It was found to vary in the range 72- 1192 embryos peryear.
21- The histology of The testis and spermatic duct were studied Through The examination of perepared series of sections.
It was found that the mature testis dose does not show cyclic variations as that of other teleosts.
The testis is composed of a large number of ampullae that lie around a median core of convoluted tubule.
The ampullae that lie near the periphery of the testis contain earlydevelop- mental stages of the germ cells.
Those that lie near the centre of testis are mature ones and each contain one spermatophore.
22- The histology of the ovary and ovarian duct was studied in the resting and gravid state through series of prepared sections.
It was found that the resting ovary contains degenerating and young ovocytes that surround an intraovarian cavity.
The latter cavity is surrounded by an ovigorous fold .
The gravid ovary on the other hand, has a more developed secretory ovigorous fold and developing embryos that are surrounded with yolk in their respective follicles.
23- Samples of the fish were collected from different localities in the Nile Delta. A preliminary comparative investigation was made on representative specimens from each sample concerning their size 5 food and maturity.