VARIATION IN FORM. 37 



and, although these points. are so small as to appear like mere granula 

 tious, they are seen under the microscope to have a perfectly definite 

 form and to be directed backward (PI. Ill, fi[gs 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, bat these may vary in number from 

 two or three in the Flicker ( CoZapies, P1..II, fig. 10), up to thirty or forty 

 in the Eedhead {Melanerpes, PI. II, flg. 2). One specimen of Flicker, 

 labeled Golaptes hybridus, PI. 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 adjilt 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 bairdijTl. 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 [Dryoliates pubescens, 

 PI. Ill, 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 skuU, although the Downy is a long-tongued bird whose hyoid runs 

 beneath the 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 gr^at changes take 

 plade 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 {Geophlceus scapularis,'P\. II, 

 fig. 11), and Flicker { Golaptes auratus or G. chrysoides, PI. II, fig. 10), in 

 which the tongue is armed with two or three points on each side; pass 

 through the Pileated Woodpecker {Geophlceus pileatus, PI. II, flg. 9). 

 into the White-headed Woodpecker {Xenopicus albolarvatus, PI. 11, 

 fig. 8^. and Downy Woodpecker (Dryobates pubescens, PI. II, flg. 4.), 



