Egg-Follicle of Culex

Abstract

1. When a newly emerged mosquito is fed on food other than blood, the nuclei of all the cells of an egg-follicle pass through the synizesis stage. After three to four days feeding on artificial food the nuclei of the nurse-cells become differentiated from the nucleus of the oocyte. The egg-follicle does not develop further on artificial food. 2. A feed on blood is essential for the deposition of yolk and the secretion of membranes. 3. The nucleolus of the oocyte is an amphinucleolus and consists of proteids and nucleinic acid as shown by the very interesting changes in its staining capacity. 4. The irregularity of the nuclear membrane of the germinal vesicle is due to the pressure of coarse yolk-granules and cannot be interpreted either as indicating a direct participation of the nucleus in the formation of yolk or as an artifact due to 5. The yolk-granules do not arise necessarily first in the neighbourhood of the nucleus. 6. In the germinal-vesicle stage the nucleus enlarges considerably in size, and its chromatin is present in the form of very small granules. 7. When the oocyte has almost reached its full size the germinal vesicle shrinks considerably in size and takes its position at the anterior end. The ‘definitive nucleus’ from which the polar bodies and the female pronucleus doubtless arise appears in the centre of the germinal vesicle. The ‘definitive nucleus’ has a very definite membrane within which is a deeply basophil mass of chromatin. 8. The outer portion of the germinal vesicle merges into the cytoplasm of the oocyte. It is difficult to associate this with the nutrition of the oocyte as it takes place when the oocyte has almost reached its full size and yolk-formation is practically complete. 9. The structure and the development of the chorion, the vitelline membrane, the striated collar, and the micropylar apparatus have been described. 10. The micropylar tube develops a short time before fertilization. It degenerates immediately after the egg is laid and is absent in the laid egg. It is thus that it has escaped notice so long. 11. As a rule copulation does not take place in captivity, but in two cases I observed that the spermatheceae of females confined with males contained a large number of spermatozoa.