Skip to main content
Fig. 9 | Evolution: Education and Outreach

Fig. 9

From: The Evolution of Complex Organs

Fig. 9

Varying levels of complexity in the visual organs of living species as illustrated by H. W. Conn in 1900: A a simple, flat patch of pigmented cells connected to nerve fibers (see also Fig. 4C); B a slightly more complex pigment cup as found in the limpet Patella, which does not form an image but provides information about the direction of incoming light; C a pinhole camera-type eye filled with water as found in Nautilus; D a camera-type eye with a large lens filling the cavity; E a camera-type eye with a basic lens and cornea as found in the marine snail Murex; F a complex camera-type eye with a cornea, lens, iris, and retina as in a cuttlefish. This shows visual organs as they occur in contemporary species—none is ancestral to another, and this does not necessarily reflect a historical series of steps in the evolution of complex eyes (see Fig. 10). It does, however, indicate that eyes of varying complexity, such as would have been found in intermediate steps during complex eye evolution, could have been—and still are—functional for organisms living in different conditions. Note that these images are not drawn to the same scale. Modified from Conn (1900). For another classic example of this kind of diagram, see Salvini-Plawen and Mayr (1977)

Back to article page