STUDIES IN THE RETINA. 467 



sold (cf. Figs. 23 and 27), and (3) passing in fine threads on to tlie outer 

 limb ; the striae wliich continue them are obscured by the internal reticulum. 



Fig. 11. — A diagram of the same showing the surface arrangement of the 

 threads ; tlie symmetry is, however, seldom so complete on the inner limb. 

 The threads thicken towards the tip of tlie rod. 



Fig. 12. — Tangential section through a group of rods of a salamander after 

 three hours' exposure to intense light. The cross-sections compare with 

 Hansen's section, Fig. 7, b. Among the rods is the nucleus of a dislocated 

 pigment cell, from which all the cytoplasm and pigment have been absorbed. 



Fig. 13. — From a toad fixed in boiling corrosive sublimate, a, b, show 

 a thick basket-like reticulum ("Faserkorb") of inner limb near the ellipsoid ; 

 c, part of a rod broken away, and showing the longitudinal threads beaded 

 with dots of staining matter; d, a Schwalbe's rod with threads apparently 

 running over the deeply stained ellipsoid and on to the outer limb ; e,/\g, 

 sections of rods cut at difi"erent angles ; from c iof what appears to be a 

 homogeneous rind is seen; h, a rod 9 /i thick, with a "rind" l'5ju thick; 

 part of the same in i, as interpreted when examined under high magnifica- 

 tion (1500 times; apoch. 2 mm.; N.A. 1"4, comp. oc. 12) ; _;', a part of a 

 cross-section, showing the material of the rind fitting into irregular spaces 

 of the reticulum; k, cross-section of a narrow rod 5 /i thick. 



Fig. 14. — Optical section of a rod from the other eye of the same animal ; 

 the "rind" seen only on one side. 



Fig. 15. — Salamander (boiling corrosive sublimate) : a, the upper parts of 

 a rod, showing dark body in or on ellipsoid, flattened like the latter against 

 the transverse membrane (see Fig. 1), and from this body two staining 

 threads descend on the outer wall of the rod ; /;, ellipsoid, egg-siiaped in 

 young cone; c, the same witii its shape adapted to its position, and with mass 

 of staining material in contact with it ; d, e, the same ; /, g, ellipsoids in 

 rods and in their definitive shapes, with dense staining matter condensing on 

 them (cf. Fig. 10). 



Fig. 16. — Toad (strong alcohol) : a, two condensed rod-nuclei protruding 

 through the mem. lim. externa, and a vesicular cone-nucleus in contact with 

 the outer reticular layer ; 6, the same, with similar vesicular nuclei, one in 

 the middle, and one in the outer, nuclear layer. 



Fig. 17. — The same, condensed rod-nuclei with fluid vacuoles in the inner 

 limbs, as if exuded by these nuclei. 



Fig. 18. — Axolotl (Perenyi) ; a condensed rod-nucleus with a much Urger 

 vesicular nucleus above it (of. also Fig. 23). 



Fig. 19. — The same; a rod forced farther than its neighbours into the pig- 

 ment, apparently by the intrusion of fluid into the inner limb, thereby dis- 

 placing the ellipsoid. 



