10. I have predicted that the average size of the brain cavity will be found to be smaller and of less capacity in a tame turkey than it is in the wild one. In the case of this class of domesticated birds, as pointed out above, this would seem to be no more than natural, for the domestication of the turkey has not been of such a nature as to develop its brain mass through the influences of a species of education; its long contact with man has taught it nothing—quite the contrary, for the bird has been almost entirely relieved from the responsibilities of using its wits to obtain its food, or to guard against danger to itself. These factors are still in operation in the case of the wild types, and the advance of civilization has tended to sharpen them.
From this point of view, then, I would say that mentally the average wild turkey is stronger than the average domesticated one, and I believe it will be found that in all these long years the above influences have affected the size of the brain-mass of the latter species in the way above indicated, and perhaps it may be possible some day to appreciate this difference. Perhaps, too, there may have been also a slight tendency on the part of the brain of the wild turkey to increase in size, owing to the demands made upon its functions due to the influence of man's nearer approach, and the necessity of greater mental activity in consequence.
Recently I examined a mounted skeleton of a female wild turkey in the collection of the United States National Museum, and apart from the skull it presented the following characters: There were fifteen vertebræ, the last one having a pair of free ribs, before we arrived at the fused vertebræ of the dorsum. Of these latter there were three coössified into one piece.
The sixteenth vertebra supports a pair of free ribs that fail to meet the sternum, there being no costal ribs for them. They bear uncinate processes.
Next we find four pairs of ribs that articulate with hæmapophyses, and through them with the sternum. There are two free vertebræ between the consolidated dorsal ones and the pelvis; and the pelvis bears a pair of free ribs, the costal ribs of which articulate by their anterior ends with the posterior border of the pair of costal ribs in front of them.
A kind of long abutment exists at the middle point on each, there to accommodate the articulation. There are six free tail vertebræ plus a long pointed pygostyle. The os furcula is rather slender, being of a typical V-shaped pattern, with a small and straight hypocleidium. With a form much as we find it in the fowl, the pelvis is characterized by not having the ilia meet the sacral crista in front. The prepubis is short and stumpy. The external pair of xiphoidal processes of the sternum are peculiar in that their posterior ends are strongly bifurcated.
Plate VII