I2 9 



Around the whole ovary there is a delicate 

 nucleated sheath. 



Each follicular tube contains one or more egg- 

 follicles in different stages of development. In the 

 freshly-hatched mosquito each follicular tube contains 

 an undeveloped egg-follicle. As this develops, a second 

 and a third undeveloped follicle appear above it, which 

 again undergo development into mature eggs. The 

 follicle at first consists of two to four large cells, with 

 large nuclei surrounded by a single layer of smaller 

 epithelial cells (Fig. 47). 



The central cells then increase in size and number, 

 so that many very large cells are contained in the now 

 enlarged follicle. The surrounding epithelial cells also 

 become larger, and rapidly increase in number so as to 

 form a layer of regular cubical cells surrounding the 

 follicle. The central cell nearest the ovarian tube 

 is the ovum, the rest are nurse cells, and eventually 

 disappear. Both the ovum and the nurse cells in- 

 crease greatly in size. 



Frequently in Anophelines a large portion or the 

 whole of the adult ovum consists of a mass of Sporozoa. 

 These consist of numerous small cysts, each containing 

 eight round or crescent-shaped bodies, each with a 

 central chromatin spot (Fig. 48). 



The ovarian tube arises in the centre of the 

 ovary, and receives on all sides the follicular tubes. It 

 is lined with a single layer of small cubical epithelium. 

 After passing out of the ovary, a considerable number 

 of striated muscular fibres are arranged in a loose net- 

 work around it, and pass from it to surrounding 

 structures. 



The spermatheca consists of a chitinous sac, with 

 large cells lying externally. These resemble the cells 

 of the cuticle, and contain droplets. They do not 



