1006 



REPORT OF NATIONAL MUSEUM, 1895. 



known to happen in Farus carolinensis, the only species in which I 

 have examined the young and traced the growth of the tongue; but the 

 tongues in this group are so siniihir that I have ventured to generalize 

 from an observation, which is, I admit, a very bad practice — where the 

 epidermal sheath of the tongue is perforated in front, allowing the 

 cartilaginous anterior portions of the ceratohyals to project through. 



The smallest and simplest style of tongue is found in some of the 

 fish-eating birds, those which, like the cormorant and pelican, gulp 

 down their food whole, and here tongue and hyoid are mostly, or 

 entirely, in the soft pouch. Flesh eaters, too, have comparatively sim- 

 ple tongues, and so have many of our little song birds, such as the 

 thrushes; and as this type of tongue is the ground plan on which much 

 more complicated tongues are found, it will serve as a good starting 

 point. The tongue of the robin is rather thin and horny, somewhat 

 thicker toward the base, or hinder portion, slightly split or feathered 

 at the tip, and provided at the back with a row of fleshy backwardly- 



directed spines. With the 

 excejjtion of these spines, 

 whose purpose seems to be 

 to start food in its downward 

 course, this tongue bears no 

 evidence of adaptation to 

 any particular kind of food. 

 This style of tongue, thin, 

 slightly cleft, and more or 

 less feathered at the tip, may 

 be called the typical pattern 

 for thrushes, warblers, and 

 the great host of our North 

 American birds. An almost endless number of tongues may be derived 

 from this simple pattern by slight changes in proportions, amount of 

 curvature, number of posterior points, and extent of feathering. Trim 

 off the tip a little and curl up the edges, and we have the tongue of a 

 shore lark (Plate 1, fig. 12) ; lengthen the tongue and feather it more at 

 the tip, and we have the tongue of a rusty blackbird, and between these 

 two we have no end of varieties. Still, among all these there is no special 

 modification hinting at adaptation to some particular kind of food, for 

 most of our small birds have considerable latitude in the way of diet. 



Not only is there much specific variation in birds' tongues, but there 

 is also a considerable amount of individual variation in the degree of 

 feathering or whipping out of the tip. Part of this is due to wear, for 

 some birds, like some people, appear to use their tongues more than 

 others, with a consequent loss of the delicate fringing at the tip, but 

 part of it is due to natural variation, for the unworn tongues of two 

 birds of the same species may have a very diff'erent aspect. Whether 

 or not the outer sheath of the tongue is molted, as some birds shed 



Fig. 2. 



