1909. | LIFE-HISTORY OF THE AGRIONID DRAGONFLY. 209 
this time the heart is beating vigorously, at about 100 pulsations 
per minute. The pedicel is then seen to be slightly removed from 
the egg, owing to the bulging out from the egg of an extremely 
fine membrane which is evidently extended with fluid. This 
membrane continues to expand until there is a gap of about 
-15 mm. or even more between the pedicel and the rest of the 
shell. It is noticeable also that the pedicel is not carried up in a 
line with the axis of the egg, but rather dorsally to the axis, and 
although this process was only watched in two or three cases 
I believe that the direction of expansion of the membrane is 
perfectly definite. 
This carrying up of the pedicel and the formation of the vesicle 
occupies one or more hours, and except for some occasional shght 
writhing movements of the gut and of the abdominal segments 
within the shell no other change is noticeable during that time. 
The vesicle is, in fact, formed many hours before the pronymph 
begins to emerge. Some time after the formation of the vesicle 
a pulsating organ appears in the head in the region of the mouth ; 
and one or two hours after this organ begins to pulsate, the head 
of the pronymph begins to expand into the vesicle. It takes the 
shape of the passage, losing all semblance of a head, and slowly 
fills the vesicle until it once more touches the pedicel. All this 
time the pulsating organ continues to beat at about 28 beats per 
minute. 
As the head begins to enter the vesicle the walls of the latter 
bulge slightly, showing that they are extended by fluid which is 
being compressed by the head. A]most as soon as the head com- 
pletely occupies the vesicle the membrane bursts along the dorsal 
edge of the pedicel and the enclosed pronymph slowly comes out. 
Just previous to this body-movements are more noticeable, and the 
tenth abdominal segment moves round so as to be in line with the 
others; but until the membrane bursts, no part of the shell is 
unoccupied. 
The pronymph appears to flow out of the shell at the start, but 
almost immediately it exerts itself and wriggles from side to side. 
It comes out in exactly the position in which it has lain in the 
shell; the lamelle, bent under the body, coming out points first. 
The lamelle straighten out more or less once the larva is clear of 
the shell, but the legs and mouth-parts remain outstretchea and 
directed backwards. 
From the moment of its escape the pronymph—a helpless 
cripple—shows active writhing movements, and within two or 
three minutes the skin on the back of the thorax splits along the 
median line and a moult takes place. The posterior abdominal 
segments contract and expand and gradually creep up inside the 
pronymph skin, drawing the lamelle out of their sheaths. As the 
abdominal segments press forward, the thorax becomes arched up 
and the head bent down. ‘The pressure in the dorsal region of the 
thorax ruptures the skin along the median line, and the thorax 
rises up through the split. In doing soit ruptures the skin further 
