Pomona College, Claremont, California 51 
floor of the diaphragm. It is elongated transversely, the two 
rounded ends being composed of a surface layer of cells with deeper 
fibers. Some of the fibers form a commissure. From each end of 
the brain two bundles are given off; one on each side passes to the 
lophophore. Sensory bristles were seen from the tentacles. Dorsal 
sense organs as described in other forms are absent in this. 
Stiasny, 1905, shows the ganglion of Pedicellina but with no 
detail. Retzius, 1905, shows the sensory nerves in the surface of 
Pedicellina. These sensory cells bear bristles and are connected 
with nerve strands which form a wide network of fibers. Sensory 
cells were found in the tentacles. 
Assheton, 1912, found the nervous system in two species of 
Loxosoma. The branches are figured and sense cells are mentioned 
on the hypostome, lophophore and tentacles. 
I have been able to study the reactions of two Pacific coast 
species of endoproctans. In Barentsia gracilis Hincks, the condi- 
tions are much as in Pedicellina. The ganglion is small and in the 
usual position. The animals are colonial with narrow strands con- 
necting the individual members of the colony; the muscular bases 
of each individual cause them to rotate in an active manner. Gen- 
eral conditions in Myosoma spinosa Robertson are similar except 
that the whole stem is flexible. In Barentsia the polype at the 
end of the stem is movable at its stalk. The ganglion is much as 
Nitsche describes. There is some indication of sense cells as shown 
by Harmer as demonstrated by the methylene blue method although 
I never obtained a perfect picture. The tip of the stem is slightly 
smaller where it joins the body of the individual and methylene blue 
shows bipolar cells at this point. Along the stem there are sensory 
pits which are the only breaks in the strong chitin-like covering of 
the ten elongated cells of the stem. In Myosoma, in place of the 
pits on the skin there are well developed hollow hairs much like 
those of arthropods. 
Tactile or other stimuli may cause a rotation of the stems with- 
out a contraction of the tentacles, but severe stimuli will also cause 
the tentacles to contract. Stems with their tips cut from the body 
continue to rotate when stimulated. Movements of the body 
of the polype on the stems may be caused by tactile stimuli. The 
effects of stimulation may be carried from one polype to another 
through the connecting stems. One polype in line with others 
may be fatigued so that it will not carry the stimuli to others. 
The stems and bases of both species seem capable of exciting 
movements of the individual as a whole better than the tentacles or 
body. In the rotating movements the tentacles are not often re- 
tracted unless the stimulus is very severe or the tentacles them- 
selves are touched. 
The control of movements of the tentacles and body are prob- 
ably centered in the ganglion. The excitation to the rotation of 
