REPORT ON THE SCHIZOPODA. 71 



magnifier, without any furtlicr preparatiuii. In .spirit specimens, somewhat greater 

 difficulty attends the research, since the transparency of the integuments, as also tliat of 

 the organ itself, is considerably diminislied by the action of the alcohol. 



The organs, when isolated (see PI. XII. fig. 26), are found to consist of perfectly 

 globular bodies, with a very compUcated structure, bearing, in some particulars, great 

 resemblance to that of the eyes in vertebrates. A rather thick and elastic cuticle forms the 

 outer envelope of the organ, which, moreover, in fresh specimens is coated with a beautiful 

 red pigment in its posterior half, whereas the front portion remains quite pelluc;id. On 

 closer examination, these two portions are found to fit as it were into each other, without 

 being actually connate, and on dissecting alcoholic specimens, the two hemispheres will 

 even readily separate from each other. At the junction, a glistening ring may be seen 

 internall}-, encompassing in the middle a highly refractive lenticular corpuscle. The 

 posterior hemisphere is filled up with cellular matter, in the midst of which lies embedded 

 a flabelliform bunch of exceedingly delicate fibres, exhibiting in fresh specimens a most 

 beautiful iridescent lustre. To the equatorial zone of the organ, moreover, two or three 

 thin muscles are attached, admitting, to a certain extent, of its being rolled to and fro. 



The above described parts are, it is true, of such a nature as might readily lead one 

 to assume that these organs are highly developed eyes. The lenticular corpuscle in 

 particular presents, both as regards its structure and its position, a striking resemblance 

 to a true eye-lens. The glistening ring too that surrounds it might easily be taken for 

 a kind of iris. The diaphanous front of the organ likewise and the red pigment coating 

 of the hinder part, as also the arrangement of the muscles for moving the whole organ, 

 would seem to favour such an assumption. 



Notwithstanding this great resemblance to visual organs, researches conducted with 

 the living animal have convinced me that none of these organs are coadjutory to sight, 

 but that they all together constitute a very complicated and peculiarly developed luminous 

 or phosphorescent apparatus. 



It has already been stated by W. Thompson that these Crustacea are highly luminous 

 at night, and for this reason he suggested for them the genei'ic name " Koctiluca." I 

 myself have several times had opportunities of testing the accuracy of this statement as 

 regards the Norwegian species of the family, and have convinced myself that the animal 

 is able, by varying the movements of the organs, to increase or diminish tlie light at 

 wdl. The chief light-producing matter I have found to be the fibrous fascicle lying in 

 the centre of the globular corpuscle. Even if the organ be crushed, and this fascicle 

 extracted, it still continues to give forth a comparatively strong phosphorescent light 

 when seen in the dark. The lenticular corpuscle placed just in front of this fibrous 

 matter may, I conceive, act as a condenser, producing a bright flash of light, the dii-ection 

 of which admits of being changed at the will of the animal, by simply rolling the organ 

 by means of its muscular apparatus. The pigment-coating of the hinder portion, and 



