Journal 



OF THE 



NEW-YORK MICROSCOPICAL SOCIETY. 



Vol. III. JULY, 1887. No. 3. 



THE COMPOUND EYE OF VANESSA 10, L. 



BY LUDWIG RIEDERER. 

 {Given May tth, 1887.) 



In making a full series of continuous sections through the 

 head of an insect with compound eyes, a lepidopter for instance, 

 if we begin in a plane adjacent to and parallel with the front, 

 the first sections of either of the compound eyes will be tangen- 

 tial to the globular mass of the combination. As the cutting 

 approaches the centre of the combination, the sections will even- 

 tually lie in the plane of some of the "ommatidia," which all di- 

 verge somewhat in the manner of the radii of a sphere, and these 

 may be called radial sections. The term ommatidium, or little 

 eye, is the name given to each entire slender column, with its 

 component parts of lenses, pigment, nerve-fibres, and layers, 

 which parts render it in reality a distinct organ of vision. The 

 multitudes of these ommatidia, standing side by side, in some 

 instances amounting to many thousands, combine to form the 

 globular mass of the compound eye. 



Explanation of Plate 8. 



Fig. 1. — Portion of a radial section of the compound eye of Vanessa lo, L. : h, hairs 

 upon the cornea ; cf, cornea-facets ; cr, crystalline cones ; pg, pigment-layer ; 

 nr, nerve-rods ; rt, separated layers of the retina ; sc, sclaera ; rm, enlarged 

 ends of the rhabdoms in pigment ; on, fibres of the optic nerve ; ga, ganglion- 

 cells ; 1, 1, 1, 2, layers of brain, or optic nerve. 



Fig. 2.— Three ommatidia, with the nerve-rods and crystalline cones slightly separated, 

 the various portions being indicated by the same lettering as that of Fig. 1. 



FiG. 3.— The exterior surface of three cornea-facets. 



Fig. 4. — A longitudinal section of a crystalline cone. 



Fig. 5.— a transverse section of a crystalline cone. 



Fig. 6.— a transverse section through the central portion of a nerve-rod, with the cen- 

 tral rhabdom, surrounded by six retinulse. 



