70 Journal of Entomology and Zoology 
4. A ring about the anal end of the trunk into which dorsal 
and ventral tracts lead. 
5. A ring about edge of prae-oral lobe, joined at each side to 
the ganglion and in median front region by three main tracts run- 
ning in mid-dorsal line. 
6. A diffuse plexus of fibers at the base of all the epiblastic 
layer, including fibers of ventral collar region, which pass forward 
and dorsally to meet the ganglion. 
Ineda, 1901, found no collar, nerve ring or dorsal or ventral 
commissure in the larva. He also failed to make out presence of 
the peri-anal ring. If present it is represented by a small number 
of parallel fibers. The main nerves were three in number close to 
each other and parallel along the mid-dorsal line of the trunk but 
confined to only a few sections posterior to the first pair of tentacles. 
There was found however a very complex and beautiful system of 
nerve fibers seen on the prae-oral lobe. Fibers are very numerous 
and fine and radiate from the ganglion on all sides towards the free 
margin of the prae-oral lobe. In the median line and anterior to 
the ganglion fibers are three long parallel strands on which the 
apical sensory spot is situated, not far from the ganglion. After 
passing through the sensory spot strands fray out into fine fibers 
which continue to the free margin of the prae-oral lobe. Fibers 
from the ganglion do not show a regular radial arrangement, but 
arise from the lateral edge of the ganglion and soon take an anterior 
direction. Sometimes near the ganglion there is an anastomosis of 
fibers, but probably more apparent than real. There are nerve end- 
ings in the prae-oral ciliated belt. There is probably an incomplete 
development of nerve elements in the collar and trunk region. He 
finds no neuropore and believes that Masterman’s structure is due 
to contraction. 
De Selys-Longchamps, 1902, gives a rather complete descrip- 
tion of the nervous system. The central ganglion is a dorsal ex- 
pansion of the epidermis with fibrillar substance below the surface. 
The depression which Masterman calls neuropore is not such a 
structure. There are three cords of the nervous system, the median 
is most developed. The apical organs are organs of sense. 
BIBLIOGRAPHY 
Andrews, E. 
1900. On a New American species of the remarkable animal Phoronis. 
Ann. Mag. Nat. Hist. vol. 5, pp. 445-449. 
Benham, W. B. 
1889. The Anatomy of Phoronis australis. Q. Jour. mic. sc. vol. 30, pp. 
125-158, pl. 10-13; N. syst. pp. 133-135. 
Caldwell, W. H. 
1883. Preliminary note on the structure, development and affinities of 
Phoronis. Proc. Roy. soc. vol. 34, pp. 371-383, 1 fig. 
