1928] 
Nervous Physiology of Dragon-Fly Larvae 
185 
animal as that of a vertebrate to its possessor. From the above 
data it is possible to draw the following conclusions: 
1. The abdominal ganglia of dragon-fly larvae control res- 
piratory movements and abdominal movements generally, but 
this control is so distributed between them that the destruction 
of one or two does not permanently interfere with respiration. 
2. The seventh or terminal abdominal ganglion not only 
has a greater part of the control of respiratory movements than 
do the other ganglia, but it also is the seat of the reflex involving 
the movements of the cloacal spines and probably of the cloacal 
valve. 
3. Each thoracic ganglion controls the actions of the legs 
attached to its segment. It also has something to do with 
equilibrium. 
4. The suboesophageal ganglion controls the reflexes of the 
mouth-parts, and without it they cannot act. But the ganglion 
itself receives no direct stimuli, excepting possibly, those that 
come through the mouth-parts themselves. Its responses are 
initiated by stimuli which come through the brain or from other 
parts of the nervous system. 
5. The brain is the sensory, directive, and associative 
center. Without it responses to visual stimuli cannot take 
place, and all coordinated spontaneous movements are inhibited. 
It also serves in some way as an organ of balance and orientation. 
The mouth-parts cannot act selectively without the brain. In 
short, the real brain of the insect consists of both the sub and 
the supraocsophageal ganglia. The former is the motor, the 
latter the sensory mechanism. 
Literature 
Baldus, K. 
1924. Untersuchungen fiber Bau und Funktion des Gehir- 
nes der Larve und Imago von Libellen. Zeits. Wiss. 
Zool., vol. 121. 
Hilton } W. A. 
1911. Some Remarks on the Motor and Sensory Tracts 
of Insects Journ. Comp. Neur. XXI, No. 4. 
