Luminosity and its Origin in a South Africaii Earthworm. 207 
be detected in some, and, in a few, this was well marked. After a time all 
these cells became disintegrated, and, soon after the commencement of this 
process, the whole of the contents of the cell became scattered about in the 
surrounding clear fluid. 
Other cells, fewer in number and smaller, were also found, circular in 
outline with a clear border and small inclusions in the centre, and appeared 
to be earlier stages in the formation of the large cells. 
More numerous, and entirely devoid of inclusions, were numbers of much 
smaller cells, with relatively large nucleus and irregular outline. Some of 
these showed active movement, when observed in the fresh condition, either 
in a hanging drop or under a cover-glass. 
In addition to these there were frequently observed gregarines of at least 
four different species. In several instances there were also i^resent the 
typical pseudo-navicellae or spores of the gregarines, and these were often 
seen associated with groups of the smaller cells above referred to. 
Nature and Cause of the Luminosity . 
The amount of luminous fluid discharged varies very considerably, both 
according to the extent of the irritation and the condition of the animal, but 
the intensity of the luminosity appeared to be always in proportion to the 
quantity of the fluid. A quantity, about the size of a pin's head, when 
placed on a slide, maintained its luminosity for a few minutes only, but, 
when the discharge was abundant, as, for instance, when it covered an area 
the size of a sixpence or even overflowed the slide, it retained its luminosity 
for over an hour. When a small quantity was at once shaken up in about 
20 c.c. of water, the water became faintly luminous, and retained its lumi- 
nosity for over two hours. The intensity of the luminosity may be judged 
by the fact that moderately large print could be made out in the dark room 
when close to the light. When left on a fairly slow photographic plate 
(Ilford ordinary) for about half a minute, the blacking of the plate pro- 
ceeded on development in a normal way for correct exposure. 
The luminous fluid could be examined microscopically in a dark room ])y 
the aid of its own light. This examination did not, however, at first prove 
so instructive as might have been expected, for the light given off presented 
the appearance of a uniform glow without any differentiation. This was 
due apparently to the fact that the light was produced during the process of 
the breaking up of the granular cells already mentioned, and the scattering 
of their contents. That these contents were still capable of giving out light 
after discharge was evident from the fact that light was produced after all 
the cells had been disintegrated, and that the luminous fluid, after being 
shaken up in water and passed through filter paper, was still luminous. 
Though the fluid was repeatedly examined under the microscope with 
varying magnifications without any differentiation being detected, on one 
