AMPHIOXUS. 303 
The brain has a single ventricle or cavity and two pairs 
of cranial nerves. The spinal cord gives off paired spinal 
nerves. The dorsa/ nerves are sensory, the ventral are 
motor, and they do not join. 
Fig. 216.—MEDIAN SECTION OF BRAIN OF AMPHIOXUS. 
(After Kurrrer.) 
Neural Tube. Ganglion Cells. 
Unpaired 
Olfactory 
Lobe. 
Pigment Spot. 
Infundibulum. Cerebral Vesicle. 
The front wall of the brain has a simple unpaired mass 
of pigment, probably a very simple eye. Over 
the brain there is a pit or depression. called 
the olfactory pit. 
Sensory. 
Fig. 217.—OBLIQUE SECTION oF AMPHIOXUS THROUGH THE 
PHARYNGEAL REGION. 
Notochord. 
Dorsal Blood-vessel 
paired). 
Nephridium. 
Ceelomic Canal. 
B 
ranchial Blood- 
vessel." == 
. ‘ 
Branchial Blood- Branchial Bar. 
vessel. 
Branchial Bar, 
Skeletal Plate. 
Ventral Blood-vessel. Endostylar Coelom. 
A secondary or tongue-bar is cut through on the left, a primary bar on the 
right. The section passes along A B in Fig. 213. : 
The ccelom leads to the exterior by numerous nephridia 
which open into the atrium. They are in the pharyngeal 
region and open over each tongue-bar. There 
is also a large pair of atvio-cxlomic funnels \ead- 
ing from the ccelom into the atrium. 
Excretory. 
