IN PORICHTHYS. 47 



lar reflecting layer is clearly a special modification of the 

 fibrous connectivetissue, but its fibres are sliorter, straighter 

 and more opaqiie, and the layer as a whole is more dense 

 tlian the siirrounding tissue. 



In both the reflector and connective tissue are occasional 

 scattered nuclei. 



That this is a true reflector is readily proved by actual 

 experiment. In sections on the stage of the microscope 

 the spicular layer is markedly fliiorescent when viewed by 

 reflected light, retaining its properties after treatment with 

 histological reagents, a fact which is confirmative of the 

 supposed nature of these organs. 



The lens is the most prominent part of the organ, It 

 consists of (see cut) a spherical or lenticular aggregation 

 of cells, the central of which are approximately cubical, 

 becoming more and more lenticular or spiiidle-shaped in 

 section, towards the outside. It is more or less complete- 

 ly enveloped by a connective tissue capsule. (This last 

 was alone preserved, in my first material, the lens having 

 macerated so that no stain would bring out the nuclei, and 

 no sections revealed cell walls in it.) 



This connective-tissue capsule in some cases completely 

 envelops the organ, and then again merely forms a cup, 

 shallow or deep, according to the organ. It consists of 

 gelatinous connective tissue, the two ends of cup showing 

 some histological difierentiation. A blood-vessel connects 

 with it at the side opposite to the spicular pocket. 



In some of the organs, there occurs a layer of pigment 

 below the reflector, while in others all the pigment there 

 is occurs in isolated patches or flakes, at the side of, or be- 

 low, the reflector. Generally speaking, the organs on the 

 dorsal surface have cousiderable pigment both beneath and 

 at the sides of the reflector, those on the sides of the body 

 have less, and of those on the ventral surface, some have 



