Matt Reed who hosts a blog, DATADeluge sent this item in, a link to the entirety of Gordon Walls excellent 1942 book The Vertebrate Eye and its Adaptive Radiation, hosted on the Internet Archive. Walls book was a landmark with beautiful illustrations and well thought out prose that reflects the man. An obituary to Gordon Walls who died in 1962 is available here, where he was properly described as a “renaissance man of 20th century vision science”.
Take the time to stop by and peruse this book. You will find illustrations drawn with engineering precision (Walls was a trained engineer) applied to difficult to visualize biological structures with descriptions that hold true to this day.