Luminosity and its Origin in a South African Earthworm. 211 
the body. The utility of luminosity is apparently still more obvious in the 
underground life of the animal. Thus it is guarded in its burrow from 
attacks both in front and in the rear, and any predaceous insect, centipede, 
or other enemy, on attacking the worm at either end, would be deluged in a 
blinding mass of luminous fluid, which, in the darkness of underground life, 
would be sufficiently alarming to cause a hasty retreat. 
The behaviour of the worm also seems to indicate a defensive organ of 
this nature, for it most readily and in every case gives off the luminous fluid 
if the head or tail is slightly touched by a sharp pin or needle. The fluid 
was, as stated, sometimes ejected to a considerable distance, and recalled 
the similar, but much more definite, ejection of a mucous substance by 
Peripatus. 
The facts narrated suggest several other promising subjects of investiga- 
tion for workers in S. Africa. Other species of earthworm in S. Africa 
would probably be worth investigating from this point of view. For 
instance, in digging for worms in a garden a species was found, but only 
one example, which gave out an abundant discharge from the mouth, con- 
sisting mainly of cells such as described but showing no luminosity. Again 
the chemical nature of the luminosity is a promising line of research, as the 
material is so readily got and manipulated ; the exact nature and origin of 
the cells, which occur in such numbers, is a subject worth investigating ; 
and, lastly, the structure, origin, and possible homology of the communica- 
tions between the coelom and digestive tract. 
I have to express my indebtedness for assistance in literature to my col- 
leagues. Prof. Jolly and Mr. Van der Lingen ; to Dr. Eobertson, Grovernment 
Bacteriologist, for examination of the luminous fluid for the presence of 
bacteria ; and to Dr. Battaerd for confirmation of the fatty nature of the 
small granular inclusions of the cells. 
Summary. 
(1) A few examples of a species of luminous earthworm were found on 
the surface after heavy rains, and subsequently in quantity by digging in the 
ground. 
(2) The luminosity proceeds from a fluid discharged from the mouth, 
and, to a less extent, from the anus. 
(3) The luminous fluid consists mostly of single cells heavily laden with 
inclusions of different kinds. 
(4) The luminosity is given out by the inclusions of small size, and these 
seem to be of a substance allied to fat, by the oxidation of which the light is 
produced. 
(5) The cells arise in the body cavity, and are discharged into the 
anterior and posterior ends of the alimentary tract by definite communica- 
tions between coelom and alimentary tract. 
