NUNNELEY, ON THE RETINA. 229 
In fish there certainly exist imbedded between the deeper 
ends of the rods, and like them, resting upon the granular 
layer, a number of conoidal bodies of larger diameter than 
the rods; each consists of two portions; an oval bulbous 
part when two are pressed together, globular when they are 
single ; and a conical one of about equal length. The point 
of junciion is marked by a very fine transverse line, and where, 
commonly, but not invariably, a separation takes place. They 
reflect the light strongly, and are at first perfectly trans- 
parent, solid, and homogeneous. The conical end breaks up 
into discs, and then granules, exactly like the rods, while the 
bulb swells and becomes less transparent, then granular, often 
irregular in shape, not unfrequently it splits more or less 
completely into two portions, and then disappears in granules. 
When the conical leg has become detached and the bulb 
somewhat split, it resembles much a coffee-berry. These 
changes occur within a very short time after death. I have 
seen them take place while the part was under examination, 
within fifteen minutes after the fish had been swimming in 
the water. They occur immediately on the addition of water, 
and many other reagents. These cones lie with the bulbous end 
resting upon, and connected with, one or more granules, the 
narrow end always being outwards. They are closely con- 
nected with the rods. There does not appear to me to be 
any such regular relation in number and arrangement between 
them and the rods as is described by Hannover ; they often 
are solitary, but very commonly two are side by side, when 
they may closely adhere by their sides, which are flattened as 
by pressure, and which has probably given rise to the idea 
of their being double, but they may be separated without 
any division of structure in the greater number of fish, though 
erhaps not in all. The cones are, I believe, commonly 
single, and 1 do not think they are enclosed by any sheath 
from the choroid; indeed, in some fish they do not appear to 
reach the outer surface of the retina, being shorter than the 
rods, as in the golden carp; while in others they are quite as 
long or even longer, asin the cod and whiting. The relative 
proportion of them and the rods appears to differ in different 
fish. In the sand-dab, Platessa limanda, and the Ballen- 
wrasse, Labius maculatus the cones are comparatively few; 
while in the whiting, Merlangus vulgaris, and the little 
weaver, or venom fish, Trachinus vipera, they are much more 
numerous ; in the mackerel, Scomber scomber, they are very 
really is seen—an attempt to generalise than a record of what actually 
exists—the small ovoid bodies more resemble the coves jumeaux of fish than 
do the conoidal rods. 
