Luminous Organs of Selachim Fishes. 



561 



between the epidermis and the cutis could not be established 

 with precision on material which had been preserved in a 

 solution of formalin. Certain it is that here, too, an incur- 

 sion of large pigment-cells into this prominence took place by 

 means of the strand leading to it, and which itself is enveloped 



Fig. 1. 



Microscopical section of the luminous organ of L. rostrat'is, 



by them. This strand seems to consist of a fibrous tissue 

 admitting a nerve of considerable size. On comparing it with 

 the luminous organ described by Johann, it appears to me in 

 process of atrophy, and may possibly be met with only in a 

 state of perfect development in the fully gestated embryo, 

 afterwards becoming resorbed. 



Fig. 2 shows the luminous organ in correlation with the 

 surrounding scales. From a bulbous centre, which latter 

 represents the swelling seen in fig. 1, extend on two sides 

 some epithelial strands which are covered by pigment. 



These scales differ from the normal ones in the following 

 points : — 



(1) By having a more abundant pigmentation of their 

 pulpa, thus making the parts which these organs occupy, and 

 which are already prominent under ordinary macroscopical 

 observation, more conspicuous. 



