UG a CHARLES PauL ALEXANDER 
The nervous system 
The most important literature on the neryous system is as follows: 
Ptychoptera. Grobben, 1876. 
Dicranota. Miall, 1893:241. 
Phalacrocera. Miall and Shelford, 1897:356; Bengtsson, 1897. 
Ctenophora. Anthon, 1908: 556-557. 
Holorusia. Comstock and Kellogg, 1904: 58-59. 
In Holorusia the brain, or supra-esophageal ganglion, is composed of 
two principal lobes united posteriorly and lying above the esophagus. 
Beneath the brain and on the under side of the esophagus lies the sub- 
esophageal ganglion, which is connected with the anterior end of the 
brain lobe by the cireum-esophageal commissures. The above-named 
organs form a complete ring, or collar, around the alimentary canal. The 
ventral nervous system leads backward from the subesophageal ganglion 
on the ventral surface of the body wall. In the thorax there are four 
closely approximated ganglia representing the thoracic and the first 
abdominal segments. Beyond these and located in the abdomen are 
six abdominal ganglia. The ganglia send off four large nerve trunks. 
The condition is similar in Ctenophora and in Tipula, there being seven 
abdominal ganglia, of which the first is located in the thorax and the last 
six In the abdomen. In Phalacrocera there are eight abdominal ganglia, 
‘the first being usually found in the first abdominal segment and the 
eighth in segment 10. The head ganglia are all independent of one 
another, not fused into a complex. The longitudinal commissures between 
the first five ventral ganglia are double, and those between the eight — 
abdominal ganglia are simple (Bengtsson). In Dicranota there are like- 
wise eight abdominal ganglia, the first being located in the first abdominal 
segment and the others in segments 5 to 10, there being two close together 
in the tenth segment. 
The reproductive system 
The most important literature on the reproductive system is as follows: 
Ptychoptera. Grobben, 1876. 
Dicranota. Miall, 1893: 248. 
Phalacrocera. Miall and Shelford, 1897: 356-357. 
Holorusia. Comstock and Kellogg, 1904: 58. 
The reproductive organs appear early in the larval development. In 
Dicranota the testes lie in the ninth segment and form elongate capsules, 
