MUSEUM OF COMPARATIVE ZOOLOGY. 157 
encloses the oesophageal cell, so that no space is left on any side. The 
dorsal line does not extend as far forward as the partition, but the ventral 
line, which takes its origin from the brain, passes under the partition, 
the fibres of which spread out above it. 
The anterior wall of the chamber is grooved externally, and this median 
groove, already mentioned, is supplied with one, or often two, low papillar 
elevations on each side. The cuticula on the anterior face of the head has 
about twice the thickness of that over the body in general. The underly- 
ing hypodermis from the mouth opening upward over the anterior dorsal 
aspect of the head is composed of high narrow cells, which are contin- 
ued basally into one or more processes that are probably connected with 
nerve fibres. These relations are represented in Figure 92 (Plate VII), 
which shows a somewhat oblique section near the apex of the head. 
It is the dorsal and lateral cells that are in question, and they show in 
some places very clearly the basal processes. Two such cells more 
highly enlarged are shown in Figure 93. The fibrous masses on either 
side into which the processes pass are the anterior prolongations of the 
fibrous mass of the brain. Bürger (91, p. 637) has described these 
cells as rounded at the deep end, and he did not find their connection 
with the nervous system. 
Along this part of the head and farther ventrad on the anterior face 
minute pore canals in the cuticula are by no means uncommon, and 
once or twice in total preparations fine hairs were seen in this region. 
Without having demonstrated any connection between the canals and 
hairs, I believe they are really united, and that the mass of cells which 
is here connected with the brain is sensory in function. Just dorsad 
to the mouth opening there was found in three specimens a small per- 
fectly regular cuticular pocket about 30 u in diameter. Its nature and 
value could not be determined, but, if at all significant, it is probably 
the remnant of a larval organ. 
The striking transparency of this region in the living animal is due to 
the thinness of its walls. Everywhere but at the extreme anterior end 
the cuticula is thin, and, although the muscular layer begins in this 
region, it is insignificant. Only on the ventral surface does one find à 
mass of tissue, the brain with its capsule. The dark streak which in 
the living animal crosses the anterior chamber just in and above this 
mass is the oesophagus already described. The chamber is filled with a 
fluid in which float small scattered corpuscles of great transparency. 
Two such are shown in Figure 95, immediately below the ganglionic 
cell, cl. gn. V. 
