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TRANSACTIONS OF SECTION D. 1051 
success when the sea is very phosphorescent, for the presence of the net in the 
water excites the luminosity and scares the herring. Little is known with regard 
to the luminosity of the ‘ Pearl-sides’ of our own shores, though from its wide 
distribution this lack of information seems to be remediable. 
One of the most striking instances of phosphorescence in living fishes is that of 
the luminous shark (Squalus fulgens) found by Dr. Bennett. This is a small dark- 
coloured shark, which was captured on two or three occasions at the surface of the 
sea, It emitted without irritation a vivid greenish luminosity as it swam about at 
night and it shone for some hours after death. The phosphorescence appears to be 
due to a peculiar secretion of the skin. The eyes of the shark were more prominent 
than usual in such forms,” 
In recent times phosphorescence has generally been associated with deep-sea 
fishes. Thus in a narrative of the early part of the voyage of the ‘ Challenger’ % 
Sir Wyville Thomson mentions ranges of spots or glands producing a phosphorescent 
secretion on the body of a fish pertaining to the Sternoptychide a species of 
which (Argyropelecus hemigymnus Cocco) is included by Mr. Francis Day in his 
history of British fishes. In a new Echiostoma (one of the Stomiatide) also the 
two rows of probably phosphorescent dots along the body were red, surrounded by 
a circle of pale violet. Dr. Giinther® observes that many deep-sea fishes have 
round, shining, mother-of-pearl bodies embedded in the skin. These are supposed 
to be producers of light, and they haye been observed to be phosphorescent in two 
species of Sternoptychide. He further states that the whole muciferous system is 
dilated in deep-sea fishes, that is, fishes inhabiting 1,000 fathoms or more, and that 
the entire body seems to be covered with a layer of mucus, the physiological use 
of which is unknown ; it has been noticed to have phosphorescent properties in 
perfectly fresh specimens. 
Having thus briefly reviewed the leading features of phosphorescence in marine 
animals, a glance may now be taken at the supposed causes and purposes of this 
provision. 
I do not deem it necessary to go into detail with regard to the numerous views 
which have been advanced to account for the phosphorescence of marine organisms, 
for these range over a very wide area—from its production by electricity, the 
constant agitation of the water, by putrefaction, by luminous imbibition, to its 
manifestation as a vital action in the animals, or a secretion of a phosphorescent 
substance. Ehrenberg considered it a vital act similar to the development of 
electricity, and sometimes accompanied by the secretion of a mucilaginous humour 
which is diffused around; while others, such as Meyen, thought it only a superficial 
oxidation of the mucous coat, or a luminous secretion from certain glands. Some 
believed that a liquid containing phosphorus was secreted, and that this underwent 
slow combustion ; while others explained that it was a nervous fluid modified by 
certain organs to appear as light. Coldstream thought it was due to an im- 
ponderable agent, and that phosphorus or an analogous substance might enter into 
the organs producing it. De Quatrefages, again, affirms that it is produced 
in two ways: (1) by the secretion of a peculiar substance exuding from the entire 
body or a special organ; and (2) by a vital action independent of all material 
secretion. Panceri was strongly impressed with the importance of fatty matter in 
the forms he examined—such as Pennatula, the Meduse, Beroides, Pholades, 
Chetopteri and Noctiluce—the phosphorescence arising from the slow oxidation of 
this substance ; the nervous system of the living animal, however, being capable of 
pee a momentary oxidation more rapid and more intense, accompanied by 
ight. 
2 It will be observed that in the Protozoa the structure of the minute but 
often very abundant animals which furnish the luminosity clearly proves that 
1 Maurolicus pennantii, Cuv. and Val. : 
* The Danish naturalist Reinwardt describes a phosphorescent fish (Hemiramphus 
Jucens) from the Moluccas. ide Giglioli, op. cit. p. 503. 
3. Nature, August 28, 1873. 
* * Challenger’ Narrative, Zoology, I. part ii. p. 521. 
§ Ibid. I. vol. ii. p. 905. 
