RETINA OE LATERAL EYES OF SPHENODON PUNCTATUS. 323 
cones, the nucleus (fig. 7, nuc . 3 ) being oval and having its 
outer extremity more or less flattened against the paraboloid 
itself. 
( b ) The far cone (figs. 5, 7, F.G.) is modified in several 
ways. The outer segment (fig. 5, o.s. 4 ) is of the same 
structure as that of the various other cones. An oil globule 
is present as in the ordinary single cone, and the ellipsoid 
(figs. 5, 7, 9, ell. 4 ), in detailed structure, also resembles 
that of the single cones rather than that of the more modified 
near cone. No paraboloid is present, its place being taken 
by a definite stalk (figs. 5, 7, 9, St. F.C. ), connecting the 
distal portion of the cone with its base in the outer nuclear 
layer. In longitudinal section (vertical section of the retina) 
this stalk appears as a fiue thread, but when seen in trans- 
verse section the arrangement is much better understood. 
The stalk (fig. 9, St. F.C.) is then seen to be flattened against 
the near cone, and to be spread over one side of the latter 
like a sheath, as shown in fig*. 9 ( g ). In many of these flattened 
stalks definite fibrils can be seen cut in transverse section, 
as shown in fig*. 9 (h), and these no doubt support the stalk. 
The far cones have each a definite nucleus, as have the near 
ones, and thus the double cones have each two distinct nuclei. 
These were distinguishable in most cases and I have no doubt 
that two are always present. Howard ( 19 , p. 619) also dis- 
tinguishes two nuclei in Necturus in a great many cases, and 
does not agree with Scliultze, who states that one nucleus is 
present in the double cone. 
V. Bibliography. 
1. Bernard, H. M. — ** The Sense of Sight : Sketch of a New Theory,' ” 
4 Ann. and Mag. Nat. Hist.,’ Ser. 6, vol. 43, 1896. 
2. — •“ Studies in the Retina: Rods and Cones in the Frog and in 
some other Amphibia,” Part I; * Quart. Journ. Micros. Sci.,’ vol. 
43, N. s., 1900. 
“ Studies in the Retina : Rods and Cones in the Frog and 
in some other Amphibia,” Part II ; * Quart. Journ. Micros. Sci.,* 
vol. 44. n. s., 1901. 
3 . 
