Eye-sign, then, was studied at least 400 years. In 1911, Felix Gigot, in his Eyes of the Great Families, partially reprinted and edited by Twombly, mentioned that the pefect eye of the Racing Pigeon was divided into four circles (1) that encircling the pupil (2) that of correlation of quality, (3) the first circle of the iris, and (4) the second circle of the iris.

We would only add a fifth circle, the one on the outer edge of the iris, and call it the fine dark line circle, or choroid circle.

Some Belgians were definitely aware of the inner circle when Bishop wrote his book. They even knew of that circle's importance when found in young birds, as reported by Ell. So it is amazing that the Englishman, having a magnifying glass, which must have been of low power like our Sherlock Holmes magnifier, but also having extensive Racing Pigeon connections over a period of many years, didn't describe the inner circle. Caught up with grading pigeons according to their outer circles (the common name for the Circle of Correlation), the scouting sight. and color and structure of the iris, Bishop missed hat may be the most significant aspect of the Racing pigeon eye - its Circle of Adaptation - the Inner Circle.

R. Fleming, in his fine book on eye-sign, showing a depth of knowledge and experience which we greatly admire. nonetheless, early on in his book, describes the Cirle of Adaptation in two or three sentences, making it obvious that he's seen the circle, but then he proceeds to neglect that organ as did Bishop. Among Fleming's many beautiful colored photographs, there are only two pictures of the inner circle, but they are so blurred that these circles can hardly be distinguished as something apart from the circle of Correlation. Fleming, like Bishop, also gives an accurate cross-sectional diagram of the pigeon eye. saying that dead pigeons can show no eye-sign, he illustrates the inner circle as a ciliary growth, instead of a flanged membrane covering a sphincter muscle unique, If not to all birds, certainly to Racing Pigeons. Fleming, oreover, includes no diagrams of the different forms of the inner circle, or even a hint as to that organ's structure or function.

Bill Soderberg and Otto Meyer make the Circle of Adaption the cornerstone for ranking eyes in their eye-sign theories. This, in our opinion, is how it ought to be. This complex structure appears to us as something that was added on late in the evolution of the pigeon eye. It would, we believe, be the most likely visible organ to share a chromosomal association with another recent adaptation of the Racing Pigeon - its homing ability - Intelligence.

Since vision and homing ability were closely associated n the selective process creating this strain, it should come as no surprise that these traits are associated genetically. We will say more about this later, giving reasons for this pinion as we go along.

Soderberg ranks the black wavy and bottle-cap circles of adaptation as the central Characteristics of his #1 and #2 eyes. In the Soderberg system, which we find very serviceable and simple to use, eyes are classified Into four categories. Only the #1 and #2 eyes, the black wavy and bottle-cap (Soderberg calls the bottle-cap sawtooth or jagged) are used for breeding. Or racing; but Soderberg never races #1 eyes. They're much too rare and valuable for breeding.

With our oversimplification of the Soderberg theory we will say here that the #1 Soderberg eye also Is required to have other characteristics besides a black wavy inner circle. For example, unexpectedly, it has a less well-defined Circle of Correlation than the #2 eye. In the #1 eye the colored pigment on the iris runs over the Circle of Correlation, masking the dark concentric lines. Some of the other characteristics of the #1 Soderberg eye will be described as we go along.

The #3 Soderberg eye, which has a flat narrow inner circle, has, as with the #2 eye, a well-defined Circle of Correlation. This eye is used for racing only.

The #4 eye has no Inner circle whatever. It possesses no, or a weak, washed-out Circle of Correlation and iris structures which we will describe more fully later. The #4

Fig, 2 . The Five Main Circles of the Eye. Starting at the pupil in the center going outward (a) The Circle of Adaptation, frequently referred to as the Inner Circle, here beaded (b) The Circle of Correlation, here with two dark concentric lines; this circle, often called the Outer Circle, can be similar in color to the First Circle of the Iris, In which case it may only have faint lines of demarkation and be hard to detect. (c) First Circle of the Iris, whose color determines the primary color of the iris, here serrated (but this is different from a serrated Circle of Correlation which can also be serrated), is usually lighter in color than the rest of the iris when not the same color. (d) The Second Circle of the Iris, which contains, when it and the First Iris Circle are of different color, the larger pigment globules, or principal photoreceptors of the iris, and (e) The Dark Line Circle on the outer edge of the Iris, sometimes hidden beneath the eye cere, except to the rear of the eye - an extension of the chorold. or vascular system for feeding blood to the eye.