Fig. 12

A schematic representation of eye development in cephalopod mollusks (e.g., squid) and vertebrates: these represent the series of stages that occur during the development of individual embryos (proceeding from top to bottom) and should not be confused with the historical path followed during eye evolution in either mollusks or vertebrates. The different evolutionary and developmental pathways followed by cephalopods versus vertebrates result in eyes that are superficially similar (both are complex camera-type lens eyes) but with some major differences. Notably, the optic nerve does not pass through the retina in cephalopods, meaning that they do not have blind spots. From Harris (1997), reproduced by permission of the National Academy of Sciences of the USA