THE CHROMOSOME COMPLEX OF CULEX PIPIENS. 295 
The Keproductive Organs in the younger stages have 
already been described. In the mature ovary (Text-fig. 1) 
the egg is elongated, and is provided with a chorion, very 
beautifully sculptured, and a second membrane — the vitelline 
membrane — both of which are perforated before fertilisation 
by the micropyle. Separating one egg from its neighbour of 
the same size, or from a young egg follicle, is a chitinous 
structure (see fig. 30, f Natural History of Aquatic Insects/ 
Miall.), like a funnel in shape, which remains attached to 
the laid egg at its broad anterior end. This funnel is per- 
forated above the micropyle, and apparently serves to guide 
the spermatozoa to the micropyle. A somewhat similar 
structure is shown in Sedgwick’s f Student’s Text-book of 
Zoology/ vol. 3 (fig. 400), for the egg of Drosophila 
cellaris. The future head end of the embryo lies in the 
anterior position in the ovarian tube, as is usual in insects— the 
hind end of the egg being the first to emerge from the imago. 
Dr. Woodcock ( 5 ) expressed his opinion that an imago was 
probably capable of depositing more than one raft in the 
season. Sections of gnats, which were fixed immediately 
after depositing their rafts, showed that the contents of the 
spermathecae were by no means exhausted. Moreover, the 
gonad showed some large eggs, as well as very many small 
egg follicles, which evidence seems to support his opinion. 
The gnats, flying away after laying eggs, were perfectly 
vigorous, and showed no tendency to die. 
The three spermathecae communicate with the hind end of 
the common oviduct by three minute tubes, so that the 
spermatozoa make their way into the funnel as the egg 
passes out. 
In view of the foregoing description and the fact that 
eggs laid in captivity often produce no larvae, the first hypo- 
thesis as to the origin of the haploid number of chromosomes 
in the somatic tissues of Culex can be rejected, and this 
is justified by actual observation of the two pronuclei in 
the egg. 
The Egg. — I have not been able to observe the formation 
