HISTOLOGY OF FEMALE OEGAXS 83 



" The pericardial cells are extremely large cells lying on either side of the 

 dorsal vessel throughout its whole extent. They are by far the largest cells in 

 the mosquito, varying from 30ju, to bO/x in longitudinal diameter. They are 

 elongate or pear-shape in form, and contain several nuclei. The nuclei usually 

 show signs of degeneration. The peripheral portion of the cell stains more 

 deeply than the central portion, which contains the nuclei and small stained 

 granules. There is a considerable number of masses of a light yellowish pigment 

 resembling that found in the large visceral ganglia cells. The fibres from the 

 branches of the alary muscles pass over and around the pericardial cells to reach 

 the dorsal vessel. From their structure and situation the pericardial cells 

 appear to be of the nature of ganglion cells. 



" The Fat-hody. — The fat-body, both where it occurs as a portion of the body 

 wall and where it lies as free lobulated masses, consists of cells containing 

 numerous oil globules. The cells are of considerable size, and their borders may 

 be frequently traced as polygonal areas. The nuclei are oval in shape with a 

 central mass of chromatin and chromatin threads. Besides oil globules the cells 

 contain granules staining with hgematein, and minute droplets of a highly re- 

 fractive, dark substance, which gives the appearance of pigment. These drop- 

 lets are larger in amount in old mosquitoes than in those freshly hatched." 



THE REPRODUCTIVE SYSTEM. 



" Each ovary consists of a large number of follicular tubes whose lower ends 

 open into the ovarian tube, and whose upper ends terminate in a delicate sup- 

 porting filament (terminal filament). The apex of the ovary is formed of a 

 single follicular tube, whose filament is attached to the fat-body of the fourth 

 segment. 



" 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 sur- 

 rounded by a single layer of smaller epithelial cells. 



" 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 increase 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. 



" 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 cover 

 the whole of the surface of the spermatheca. The spermatozoa have a narrow, 

 slightly-curved head and a long tail. The duct of the spermatheca is narrow and 

 thick-walled, and contains muscular fibres. Certain large cells lie in connexion 

 with the duct externally. The mucus gland contains cells filled with secretion." 

 7 



