OVARY AND OVARIAN EGG OF ANOPHELES 403 
distorted, are still placed at reguiar intervals. In other cases, 
however, the nuclei certainly appear to be the origin of the 
muscle-bands. 
Over the greater portion of the surface of the investing 
membrane the muscle-bands radiate in the normal manner 
(fig. 28), but towards the junction with the oviduct they 
gradually become reduced to two laterally-placed bands which 
pass transversely to the long axis of the ovary (fig. 29). Finally, 
the investing membrane passes over the oviduct and the 
muscle-bands now form the circular muscles of the oviduct. 
In a similar manner the muscle-bands of the follicular tube 
membrane pass insensibly into the longitudina! muscles of the 
oviduct, inside which is found a layer of columnar cells surround- 
ing the lumen of the oviduct. 
If an ovary of a living insect is dissected out in salt solution, 
a vigorous rhythmatic peristaltic movement is noticed. This 
may be produced by the stimulus of the salt solution, but there 
is little doubt that this movement takes place in the living 
insect, at least when the eggs are being laid. The movement is 
undoubtedly due to the muscular system described, and the 
basket-work arrangement of the muscle-fibres is ideal for 
compressing the ovary and so pressing the eggs into the 
oviduct. The muscle-bands which pass from the investing 
membrane to the follicular tubes are probably of use in drawing 
the latter off the eggs, a process which takes place some time 
before the eggs are laid. 
A number of very characteristic cells are found in the space 
between the two sheaths, and also between the follicular tubes 
and the egg-follicles ; one or more is almost always to be found 
in the region of each terminal chamber, between it and the 
folheular tube membrane (fig. 25). These cells consist of large 
nuclei embedded in a mass of very much vacuolated protoplasm, 
from which fibres are frequently seen to pass. The exact 
nature of these cells I have not been able to determine, but 
T am of the opinion that they have some relation to the tracheal 
system. The fibres seen passing from them are probably 
tracheal endings, but they are so fine that it is difficult to 
NO. 259 Ee 
