LUMINOSITY. XXVn 



struck with .admiration at the luminous radiata and mollusca, while it has 

 been observed that an increase in brilliancy occurs when these animals are 

 in 'motion. Dr. Guppy has commented upon a small shrimp in the South 

 Atlantic which constantly emits a light from its ejea, while long fila- 

 mentous organs are likewise to be met with showing apparently a brilliant 

 type of phosphorescence. Among the many curious forms of development 

 of these tactile organs one is seen on a fish 'found at the depth of 2700 

 metres in the Mediterranean Eustomias obscuriis, Vaillant, in which the 

 tactile organ takes the appearance of a long' filament^ which is placed 

 underneath the lower jaw, and ends in an inflated and rayed knob-like 

 phosphorescent mass. Some marine invertebrates emit a mucous fluid 

 possessing luminous properties which are not immediately lost when mixed 

 with water or other fluids. It is not long since I heard of a gentleman 

 having purchased a lobster, which he took with him wrapped in paper, 

 when going by train from Southampton to his house, which was some hours 

 distant. On arrival his lobster was found to have been kept quite long 

 enough, and having been removed from its paper wrapper was consigned to 

 the co'ok. Some hours after, on going into the dark room wherein the 

 paper wrapper had been left, he was startled at seeing a dull blue light 

 coming from the table. Cautiously advancing, he gave the uncanny object 

 a poke with a stick, and then" found it was the piece of paper which had 

 inclosed the lobster, and doubtless had become covered with its mucous 

 secretion. 



Irrespective of this locally-circumscribed luminosity the luminosity of 

 animal substances must be slightly touched upon. General- luminosity 

 in fishes may be seen at two distinct periods— (1) during life, (2) after 

 death. The shark is one of the former which has the reputation of 

 being luminous, the light being believed to come from its abdominal 

 surface. Shoals of- fish are said to frequently emit flashes of light 

 which. are visible even at great depths. The sand-launce in some locali- 

 ties is said to be sought for by moonlight, as kt night-time their 

 silvery brilliancy is more' striking than it is by day. M'Culloch also 

 enumerates mackerel, pollack, whiting, pilchards, sardines and gar-fish as 

 being sometimes accompanied by these lights. Collett speaking of the 

 Aphia pellucida remarks that in the males in full breeding almost every 

 part of the body has a faint jprownish light, although this is nowhere col- 

 lected into larger dots, but is more distinct along the transverse impressions 

 of the muscles. Secondly, we find this general luminosity often exists for 

 some time in dead fish, commencing a short time subsequent to death and 

 continuihg until decomposition sets in. In the forms which most rapidly 

 decoinpose luminosity is most quickly developed. This is well seen in the 

 cod family, and the basket containing these fish kept for feeding the 



