210 SECTIONAL ADDRESSES. 
Luminescent pathogenic bacteria may invade the host, as described 
by Giard and Billet (1889-90), for the small marine amphipod, Talitrus, 
of which rare light-emitting examples may be found in nature. The 
affected crustacean dies in about six days. The pathogenic bacterium 
does not luminesce in cultures, but does so when inoculated into 
Talitrus. 
Luminescent symbiotic bacteria present in various light-emitting 
animals are, however, of direct interest to us, since their presence has 
been determined in luminescent organs of certain insects, cephalopods, 
tunicates, and fishes: 
Insects: Pierantoni (1914) investigated the luminous organs of 
glow-worms (Lampyrus), and found them to consist of parenchyma 
cells crowded with minute bodies having bacteria-like staining reactions, 
these bodies being also present in the beetle’s egg, which is luminous. 
He cultivated two species of micro-organisms from the organs, but does 
not distinctly establish their causal relationship. 
CEPHALOPops: We owe to Pierantoni (1917-20) and Buchner the 
discovery that luminescence in certain Cephalopods is due to light- 
preducing bacterial symbionts living in special organs of the host. 
These organs may be simple or otherwise. In Loligo the luminous 
organs, hitherto known as ‘ accessory nidamentary glands,’ represent 
the simpler type of organ, this consisting merely of a collection of 
epithelial tubes surrounded by connective tissue. In cuttle-fish 
(Sepiola and Rondeletia) the organs are more complicated, the glands 
being backed by a reflector, and provided outwardly with a lens serving 
for the projection of the light rays generated by the symbionts within 
the tubes. The symbionts are transmitted hereditarily when the 
Cephalopods lay their eggs. The symbionts of Loligo and Sepiola 
have been cultivated by Pierantoni and Zirpolo (1917-20); they 
inhabit the gland-tubes of the luminescent organs in large numbers, 
and produce light continuously, as do other luminescent bacteria in 
cultures. 
Tunicata: The Pyrosomide, all of which emit light and form 
tubular colonies, have long attracted the attention of biologists. Each 
individual in the colony possesses two fairly large luminescent organs, 
whose structure was studied by Panceri (1871-77), Kovalevsky 
(1875), and especially Julin (1909-12), who observed in the cells of 
the luminous organ riband-like structures appearing knotted here and 
there. Julin regarded the structures as mitochondria or chromidia, and 
it was left to Buchner (1914) to explain their true nature; they are 
symbiotic fungi, and are transmitted hereditarily. Buchner gives a 
detailed study of the symbiont and a review of the physiology of 
luminescence and of Pyrosomes which is well worth consulting by those 
interested in such problems. 
Fisu: Of great interest are the researches of Harvey (1922) upon 
light prduction by two species of fish (Photoblepharon and Anomalops) 
which occur in the sea about the Banda Islands, Moluccas. Their life- 
history is unknown. “They measure up to about 11cm. in length. The 
author writes: ‘ In both fishes the luminous organ is a compact mass 
of white to cream-coloured tissue, flattened oval in shape, lying in a 
