POST-EMBRYONIC DEVELOPMENT OF CULEX. yall 
is closed except when at the surface of the water it is 
opened to allow the animal to take a fresh supply of air 
into its enormous trachee. 
The alimentary canal is nearly straight. The mouth 
cavity receives the secretion of a pair of salivary glands by 
a median aperature. The narrow cesophagus opens into 
the “stomach” at the anterior end of the thorax. The 
stomach is wide and extends to the sixth abdominal seg- 
ment. In the thorax it has eight large sac-lke diverticula. 
The epithelial cells hning the stomach and its diverticula 
are extraordinarily large. The short ileum runs from the 
hinder end of the stomach to the wide anterior end of the 
rectum at the beginning of the eighth segment. It receives 
five malpighian ceca at its anterior end, the odd one being 
dorsal. The rectum is wide in the eighth segment, nar- 
rower in the last segment, and is stated by Raschke (4) * 
to be respiratory. ‘The nervous system has the typical ar- 
rangement— supra-cesophageal ganglia with optic lobes on 
their outer sides—subcesophageal ganglia and a ventral cord 
with ganglia in each of the three segments of the thorax 
and each of the first eight segments of the abdomen. 
The larva at first feeds actively and grows rapidly. 
Towards the end of larval life it becomes sluggish, and 
floats with the tip of its siphon at the surface of the water. 
Tt no longer feeds, for changes preparing it for the future 
state have rendered its jaws useless. Shortly the cuticle 
splits along the mid-dorsal line of the thorax. A pair of 
hollow, horn-hke organs, the respiratory siphons of the 
_ pupa are protruded; the trachez of the abdomen appear 
to collapse and the animal floats anterior end uppermost, 
while the pupa gradually makes its way out of the last 
larval cuticle. 
The exuvie consist of the cuticular covering of the 
* The numbers in brackets refer to the list of works at the end of the paper. 
