TKANSACTIONS OF SECTION D. 803 



In one species I found three or four isolated ones in the centre of the dorsal 

 surface of each fin. 



In section it is seen that each organ is a spheroidal hody embedded in the sub- 

 cutaneous cellular tissue, and consisting of the following- parts : (1) an outer pig- 

 mented cup with a considerable aperture (a quarter of its circumference) in front. 

 (2) A lining within the cup, consisting of a single layer of cuboidal ceUs, with 

 spherical nuclei, easily stained. (3) The anterior aperture of the pigment cup is 

 filled by a lenticular body, composed of masses of a structureless yellowish 

 material, to all appearance cuticular in nature, with small deeply-stained cells 

 between the masses. (4) From the back of the lens there projects into the centre 

 of the organ a conical plug, composed of deeply-stained cells. These are seen in 

 transverse sections to be disposed concentrically round the axis of the cone, pro- 

 ducing the efi'ect of the well-known ' cell nests ' of an epithelioma. (5) The space 

 between this plug and the cells lining the pigment cup is filled with a clear trans- 

 parent mass. In its peripheral portions this seems to be made up of thin layers 

 arranged concentrically like the coats of an onion ; whilst nearer the centre it has 

 the form of curved rods, wider in front than behind, amongst which nuclei are 

 sparsely scattered. 



In most cases a space, most likely a blood lacuna, was seen around the organ ; 

 no nerve supply could be traced out. 



It is impossible without an opportunity of examining the living animal to say 

 what part of this apparatus is the active agent in producing the light ; indeed, it 

 must be remembered that positive proof of its being a luminous organ at all is 

 still wanting. 



Of similar structures as yet described in other animals it seems to resemble 

 most nearly the photospheria of Nyctiphanes norvegica, a schizopod crustacean 

 examined by Messrs. Vallentine and Cunningham. As regards origin, these organs 

 are probably to be regarded as highly modified chromatophores ; an analogous 

 modification would be found in the thermoscopic spots recently described by 

 Joubin in another cephalopod. 



2. Bejport on the Marine Zoology of the Irish Sea. — See Reports, p. 526. 



3. Interim Report on a Deep-sea Tow-net. 



4. The Origin of Organic Colour. By F. T. Mott, F.B.0.8. 



In a complete plant of the higher orders there are three distinct schemes of 

 colour — viz., the browns, olives, and maroons of the stem and branches, the greens 

 of the foliage, and the reds, yellows, and blues of the blossom. 



These indicate a successive decrease in the amount of light absorbed, which 

 miist be the result of changes in the absorbing capacity of the molecules. It is 

 suggested that the cause of these changes may be found in the specially organic 

 phenomenon of food assimilation, and the concentration of energy in the molecular 

 structure which this implies. If such energy is stored in the form of increased 

 molecular vibration, sets of molecules will successively reach the maximum limit 

 of vibration possible to them, and will lose the power of further absorption. 

 Thus the amount of reflected light will increase as the plant attains maturity ; and 

 as the arrest of growth which accompanies the formation of blossom throws upon 

 the vibration of the molecules the energy otherwise expended upon growth, a 

 marked increase of reflected light from the flower is the natural resiUt. 



5. Remarks on the Boots of the Lemna and the Reversing of the Fronds in 

 Lemna trisulca. By Nina F. Layard. 



The roots of the various English Lemnse are usually described as identical in 

 form and structure, if, indeed, they receive any attention at all ; but a careful 



3 F 2 



