Pomona College, Claremont, California 1 
is found in the tentacles where there is a combination of sensory 
cells at the base of the sense organ. 
The retrocerebral apparatus in Hosphora consists of two glands 
lying back of the brain. They are covered with membrane and so 
not in direct connection with the brain. One of these glands is the 
pear-shaped retrocerebral sac which is clear with vacuoles. If 
this is in any way a sense organ it is a question what its function 
would be. 
In Eosphora there is a single eye on the surface of the brain 
and two slightly pigmented knobs at the anterior margin of the 
animal; these have a direct connection with the brain and must be 
sense organs, possibly something like eye spots. 
GASTROTRICHA. In 1864 Gosse described a knob on the oesoph- 
agus as the brain in Chaetonotus. Ludwig in 1875 described the 
nervous system on the side of the brain. Butschli, 1876, added 
nothing of importance and Fernald, 1890, did not see the brain in 
Chaetonotus. The clearest recognition of the nervous system was 
by Zelinka in 1890. A large brain in the head region surrounds 
the gullet above and on the sides and a pair of nerve trunks extend 
down the body. Cephalic sense hairs are directly connected with 
nerve cells of the brain. The hairs of the body may be for touch 
or possibly smell or taste. Simple eyes have been described for a 
number of species in the back part of the head, as small red spots, 
but not all species possess them. 
KINORHYNCHA. Claparede in 1863 describes a nervous sys- 
tem in this group and others at an early time also figure or describe 
something of the nervous system. Reinhard, 1887, believes that in 
most cases the nervous system was not seen by the earlier investi- 
gators. He describes and figures a ganglion on the oesophagus but 
gives no details. Zelinka, 1894, describes a circum-oral ring and a 
long ventral nerve strand. Schepotieff, 1907, describes a brain 
above the oesophagus with two connectives and a ventral strand. 
The nervous system is somewhat like that of Gastrotrichia with a 
large upper brain of a large mass of three general parts all fused. 
The ventral strand runs the length of the body but is not differen- 
tiated into ganglia but has cells along its course. Eye spots have 
been described in some species, the number being from 2-8. 
BIBLIOGRAPHY 
Butschli, O. 
1876. Untersuchungen uber freilebende hematoden und die Gattung 
Chaetonotus. Zeit. f. wiss. Zoll. Bd. 26, pp. 363-413 Taf. 23-26. 
Claparede, E. 
1863. Beobachtungen uber Anatomie und Entwickelungsgeschichte wir- 
belloser Thiere. An. der Kuste Normende pp. 90-92, Taf. 16, figs. 
