206 Trmisactions of the Royal Society of South Africa. 
water, and even dried subsequently on blotting-paper without exciting any 
discharge. A worm treated in this way was placed between two photographic 
plates in a dark room. The adhesion of the dry surface of the film prevented 
any movement of the animal, and, at the same time, induced a discharge. 
The details of this could be watched through the plate. A light spot first 
appeared at the mouth, and slowly spread backward over the surface of the 
anterior segments of the animal. Similarly, but some time afterwards, a light 
spot appeared at the anus, spreading on to the surface of a few of the posterior 
segments. The earthworm was then removed, and on developing these light 
areas appeared as a blacking of the plate (Fig. 2). In another case the 
spreading of the fluid was allowed to go further, and the whole of the body 
of the worm ultimately became enveloped in the luminous substance. Here 
also the light was observed to appear first at the mouth and anus, and there- 
after to spread over the body. To obtain further information as to the source 
of the luminosity, a worm was compressed between two plates, before the 
luminous fluid had time to spread along the body from the mouth and anus. 
The result is seen in Fig. 3, in which it will l)e noted that the luminous fluid 
has been forcibly ejected at the various parts where the body has been 
ruptured. In interpreting this result, it must be remembered that, after the 
compression, there was time for the fluid to spread to some extent between 
the closely applied plates elsewhere than at the place where the fluid was 
first ejected. It was at first supposed that the luminous substance had been 
ejected from the alimentary canal, but, as will be shown later, its actual seat 
is in the body cavity. 
The Ltimivous Fluid. 
When first extruded the luminous fluid appeared of a whitish colour in 
daylight, and could not well be detected, except with careful observation 
under a lens. If shaded by the hand, however, it could be seen to be of a 
greenish colour, and to be luminous. When examined under the microscope 
it was found to consist of a great number of cells, so densely packed together 
as to be in contact with each other. Occasionally a greater or less amount 
of a viscid mucus occurred along with these, but, though the cells were more 
or less entangled in this mucus, it apparently was not necessarily associated 
with them. There was also present in all cases a certain amount of clear, 
watery fluid. 
The greater majority of the cells were of a large size, the largest being 
about 20 fi in diameter. These were very heavily laden with inclusions, most 
of which were rounded, apparently of a fluid nature, and of a greenish colour. 
These were also of various sizes, the largest being about the size of the 
nucleus of the cell Scattered among these were small specks or granules, 
apparently of a more solid nature. 
The most of these cells showed no movement, but a slow movement could 
