240 Trochosjphsem wquatorialis. By Herr Semper. 
oral hemispliere witli the aboral (1 1, 4 1), belong to this point. 
With a broad end each joins to a hollow in the oral surface 
(4?)), then close under the skin, but yet suspended freely in the 
corporal cavity, it passes under the equatorial fringe and fastens 
itself (4/) to the aboral hemisphere by a number of long, thin 
filaments, which in their course are divided up and join the skin 
with ends somewhat broader. I have never noticed contractions 
of these ribbons : yet in appearance they correspond to the pharyn- 
geal muscles. Among them some nerves (which shall be described 
immediately) pass along, which are partly lost in them, in the part 
nearest to the hollow of junction. 
The central nerve-system consists of a large brain-ganglion, 
lying over the pharynx (if the aboral hemisphere is regarded as the 
upper, i. e. as the forehead), with deep inlets in front and drawn 
out into large points towards the back in the middle as well as on 
the sides (3 Altogether five pairs of nerves leave the brain, 
and one single (unmatched) nerve from the middle point behind (6). 
The first two (3 — 1, 2) pass, the first to the opening of the mouth and 
the head of the pharynx, the second to the front part of the circular 
fringe. The third nerve with the fourth arise in common from a 
lengthening of the brain, still they separate so soon that they cannot 
be regarded as branches of the same nerve. At first they run 
almost parallel till they reach the problematical muscle-layer and 
its hollow (4 h, c). Here it seems they both send off branches 
into this organ, but both pass on under it in their main branch. 
Then they separate ; the third nerve turns suddenly downwards at 
an obtuse angle, i. e. up towards the oral hemisphere {In; 4 — 3 h) 
and passes into a problematical organ (1 n), that will be more 
minutely described immediately. The nerve No. 4 divides into 
two branches immediately behind the muscle-band (4 a and h), 
which, passing on close by one another, end near the circular fringe 
in the eye and in a problematical organ lying close by this. The 
fifth nerve (3 — 5) begins at a short cylindrical appe]:idage of the 
brain, passes across the cavity of the body, and joins the end of 
the organ of excretion, which will be described later on. Lastly, 
the sixth single nerve crosses the equator — differing in this from all 
the remaining nerves that lie in the oral hemisphere — then exactly 
at the meridian it passes close under the skin of the aboral hemi- 
sphere (Ijp), again crosses the equator opposite the mouth (1 ^) — 
at least in its main branch — after first (6/) exhibiting a ganglion- 
like swelling of one cell, sends out on the sides symmetrical branches 
towards the encircling fringe which just here is interrupted (6 g'), 
and at last through the said main branch passes into a peculiar 
organ (6 A) lying on the oral surface. 
Of the organs of sense the eye is easily found. It Hes close by 
the equatorial fringe (1 m), and, in conjunction with the mouth and 
