380 
EDWIN LINTON 
MOVEMENTS 
The behavior of these worms is highly characteristic. When 
placed in sea water they creep about on the bottom of the dish. 
They move by means of ciUa, but the body in addition is in con- 
stant motion. The mesenchyme is soft and yielding and responds 
to every contractile movement of the body-wall. Although act- 
tively moving, the worm does not make progress in any one direc- 
tion save for a very short time. For example, it will move for- 
ward for a short distance, usually not more than its own length. 
It will then turn the head end sharply to one side or the other. 
The direction of progress being thus changed, the worm will 
move in the new direction again for about its own length when, 
in the same manner, a new direction will be taken. The result 
is that but little progress is made unless some factor, such as gravi- 
ity or light, is added. For example, if the dish is not level the 
worm will be found in the course of a half-hour or so to have 
changed its position from one side of the dish to the other. While 
they do not react immediately in any marked degree toward the 
light, in general the adults tend to move away from it. Thus they 
maybe found to have crept up the side of the dish and be clustered 
near the surface of the water in response to the action of light. 
Tn order to determine whether these worms react in any way to 
light the following observations were made. A number of them 
were left over night in a watch-glass. On the following morning 
they were, so far as T could see, as active as they had been on the 
previous day. They had all gathered at the side of the dish that 
was turned away from the hght. The side of the dish next the 
window was then darkened and the opposite side illuminated. In 
a few minutes the worms were clustered at the darkened side of 
the dish. The worms do not move in a straight line away from 
the hght, but keep up their habit of starting off in a great hurry 
for some place, but going only a length or two in any one direc- 
tion, then turning abruptly to the right or left and thus proceed- 
ing by a series of zig-zags. The result of this peculiar method of 
movement in its natural habitat must be to afford the animal a 
constant change of position, but as a rule within a limited area. 
