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Show 1890.] MR. W. K. PARKER ON OPISTHOCOMUS CRISTATUS. 45 beast ever became transformed into the quick, hot-blooded, feathered fowl, the joy of creation. Now if any one will look at the picture I have made of the half-ripe embryo of the Hoatzin, he will see that which will help him to imagine how the Reptile crept out of his lowliness and became that high and noble creature-a Bird. Of course the wings dominate everything else in the organization of the bird ; all other parts must be correlated to these metamorphosed paws. That wings were paws we see in this Reptilian bird, and the suppression of the parts of a five-fingered hand, which is so striking a character in the normal wing of a bird, wherein three digits only, and these strangely mangled and fused, are all that remain of the Reptilian fore-foot. That suppression is incomplete in Opisthocomus. In the half-ripe chick of this bird, the first and second fingers have claws as large, or nearly as large, as those of the toes ; and on the third finger, which, as a rule, in birds has only one phalanx, instead oi four (as in the Reptiles), I found in one of the embryos a definite claw, such as I have shown to exist in Struthio and Rhea • I have seen this in no other bird but these three. There is, also, what 1 have found in many birds, a rudiment, of the fourth finger ; this is a "phalanx " in this bird, it is a " metacarpal " in the chick of the common fowl and in the Carinatse generally. In Opisthocomus, and in a few other birds, the two normal proximal carpals, those that in the adult bird are always free and mobile, are, for a few days, segmented into additional elements. Thus, taking what I find in this and other birds, the bird's wrist may have all the carpals seen in Amphibia and Reptiles. 1 am familiar with nine carpals in the wrist of birds, although normally only two are permanently distinct. If these facts are not remarkable, I know of nothing that one need wonder at and admire ; they cannot be made into poetry, but they are not prosaic. Nor are there wanting, in this bird, as in others, signs of marginal and intercilary digits in the wing of the embryo; atavistic remnants or vestiges that are Reptilian and probably A m phibian "stigmata." But the more fused proximal structures that help to form the organ of flight in this bird are as remarkable as the free distal parts. This bird, which I take to be an archaic Curassoiv, an unchanged " waif" of the family from which the Cracidce arose, like the Tinamou, never lost its sternal keel; the Ratitce have lost it: they are overgrown, degenerate birds that were once on the right road for becoming flying fowl, but through greediness and idleness never reached the " goal," went back, indeed, and lost their sternal keel and almost lost their unexercised wings. Now the Tinamou has lost its tail, or nearly so ; the Hoatzin has kept its tail; the former, to make up for this, has a huge keel in his extremely long sternum, whilst the Hoatzin has a small keel on a short sternum. Both of these birds can fly a little, they are not careful to cultivate that talent, they are not birds of " understanding." Now the |