VARIATION IN FORM. 37 
and, although these points are so small as to appear like mere granula 
tions, they are seen under the microscope to have a perfectly definite 
form and to be directed backward (PI. III, figs 8,9.) They are smallest 
toward the tront of the patch, and increase in size from thence back- 
ward. 
The anterior, horny portion of the tongue is also subject to great 
variation. In most species it is armed on either side with a number of 
sharp, backwardly-directed spines, but these may vary in number froin 
two or three in the Flicker (Colaptes, P1.II, fig. 10), up to thirty or forty 
in the Redhead (Melanerpes, Pl. II, fig.2). One specimen of Flicker, 
labeled Colaptes hybridus, P1. I, fig. 1), had the tip of the tongue wholly 
unarmed; but this may have been an individual peculiarity, and if so, 
would be interesting as showing the retention in the adult of the con- 
dition found in the young. In the Sapsucker (Sphyrapicus) the tongue 
bears no spines, but two series of stiff hairs, the lower set directed out- 
ward, the upper series backward. Of course, strictly speaking, these 
hairs are simply very slender spines, and in the California Wood- 
pecker (Melanerpes formicivorous bairdi, Pl. II, fig. 1) we find an almost 
intermediate stage, the spines being quite fine, and the sides of the 
tongue, as in a few other species, furnished with a few short hairs lying 
below the spines and directed outward and forward. 
In very young woodpeckers the tongue is unarmed at the point, bear- 
ing neither hairs nor spines, although the patch of minute points on the 
upper surface is present from the first. Later on, as indicated by a 
fully-fledged nestling of the Downy Woodpecker (Dryobates pubescens, 
PL ILI, fig. 6), a species whose tongue, when adult, is armed with sharp 
barbs, “the spines are represented by short, fine, reflexed hairs, like the 
upper series of the Sapsucker (Sphyrapicus varius), Thus it would 
seem that the lateral spines are acquired after the bird has commenced 
to fly, and that they must be developed very rapidly, although speci- 
mens showing the.various stages in their acquisition are lacking. The 
growth of the hyoid must be correspondingly rapid, for in the nestling 
alluded to the ends of the epi-branchials. reached only to the center of 
the skull, although the Downy is a long-tongued bird whose hyoid runs 
beneath tind nostril into the bill. This rapid growth has been observed 
in the hyoid of humming birds, in which the growth of the bill is also 
very rapid after hatching, and it would appear that great changes take 
place in the tongue and beak about the time the young bird ceases to 
be fed and begins to feed itself. 
If woodpeckers were to be classified by their tongues we would start 
with forms like Delattre’s Woodpecker (Ceophleus scapularis, Pl, I, 
fig.11), and Flicker (Colaptes auratus or C. chrysoides, P1. II, fig. 10), in 
which the tongue is armed with two or three points on each side; pass 
through the Pileated Woodpecker (Ceophleus pileatus, Pl. I, fig. ?) 
inito the White-headed Woodpecker (Xenopicus alteloeiule, Pi. I, 
fig. 8). and Downy Woodpecker (Dryobates pubescens, Pl. I, fig. 4), 
