560 Prof. R. Burckharclt on the 



rare shark from the Mediterranean. These T had put aside 

 for the purpose of future microscopical use, pending the 

 completion of other anatomical research ; I then concerned 

 myself with this shark. Unquestionably they were organs of 

 luminosity, of the correctness of which opinion I became 

 more firmly convinced, since a splendid specimen of Spinax 

 m'ger afforded me an opportunity for confirming Johann's 

 observations. 



When, in the spring of 1898, I was working at the Zoolo- 

 gical Station in Naples, Dr. Salvatore Lobianco, with his 

 wonted kindness, seized upon the first opportunity that pre- 

 sented itself to procure for me half a dozen living specimens 

 of this species, which, however, arriving one evening, died 

 the next morning. 1 was greatly struck at the time by the 

 splendour of the spectral colours which these fishes exhibited, 

 and of which, so far as I am aware, no mention anywhere in 

 literature seems to have been made. This latter circumstance 

 induced me therefore to prepare a coloured sketch of this 

 phenomenon from these fishes. 



A later scrutiny of this sketch convinced me of the fact 

 that I had been able to observe the phosphorescence of these 

 organs by daylight, so strong was their luminous power*. 



It is not my intention here to enter into details relating to 

 the purely histological modifications of these organs amongst 

 other Selachians, feeling sure that they all share more or less 

 the type of form which Johann has ascribed to them for 

 Spinax. 



A few figures, however, which I made of Lcemargus ros- 

 troius ma) well find a suitable place here — firstly, because 

 they will prove that the organs observed by myself are really 

 identical with those of Johann ; and, secondly, they go to 

 show, as before stated, that the organs pertain to that form 

 whose morphological structure is so much affected by the 

 scales, as is the case with many of the Teleostean fishes. 



The transverse section made through the luminous organ 

 of Lceruargus rostratus (fig. 1) shows an epidermal swelling, 

 projecting crater-like above the ordinary level of the epidermis. 

 Beneath a few layers of epidermal cells of normal texture are 

 some which contain a prismatic corpuscle. The actual limit 



* It should be stated here that with regard to its outer appearance 

 Spinax has repeatedly been the victim of misrepresentation,/, i. : — 



1. In the figure which Ratinesque gives of it, by ha\ing three gill- 



openings only. 



2. Its natural colours were quite unknown to all iconographers of 



fishes, from Bonaparte to Fries. 



3. In being represented with its abdomen turned upwards in 



Moieau's drawing, without any reasons given for so doing. 



