^°189L^'] PROCEEDINGS OF THE NATIONAL MUSEUM. 171 



membrane, the external fold of cartilage becoming thus transformed 

 before the fork of the tongue is reached. 



This membrane curls upward and inward, much as one might roll a 

 piece of paper, so that toward the apex two very delicate parallel tubes 

 are formed. 



This tubular part of the tongue, formed by the curled-up membrane, 

 exists only for a short distance towards the anterior end, so that the 

 common statement that the tongue of the Humming Bird consists of 

 two parallel muscular tubes is quite erroneous. 



So also is the statement that the tubular part of the tongue when at 

 rest is drawn back into a muscular sheath. 



When the tiange is flattened out each moiety of the tongue suggests 

 a feather with the vane on one side only, a resemblance that is height- 

 ened by the fact that toward the anterior end the membrane is more or 

 less fimbriated. 



Just how much of this fimbriation is normal and how much due to 

 wear is somewhat of a question, although it is very evident that use 

 has something to do with the lancination of the membrane, for it varies 

 in individuals of the same species, and in some cases whipping out by 

 wear is very apparent. 



Dr. Gadow, indeed, speaks of specimens in which the membrane was 

 entire, but does not mention the species, and none have come under my 

 own notice in which the membrane was not somewhat lancinated. 



The width of the bordering membrane varies in different genera, 

 being for example very wide in Florisuga and very narrow in Bellona, 

 the width doubtless bearing some direct relation to tlie food of the bird. 



la a nestling of Calypte annce, shown in Fig. 6, PI. iv, the bordering 

 membrane was longer than the cartilaginous rod supi)orting it, and the 

 tongue but little cleft. 



No fresh specimens of Humming Birds have been available, but in all 

 birds examined the two branches of the tongue have more or less of an 

 outward spiral twist, as shown in Fig. 3, PI. iv, and I suspect that 

 this may be the normal condition, although it is not mentioned by 

 Gosse, who gives a very good description of the Humming Bird's tongue. 



This author states that he is unable to quite understand the action 

 of the tongue in sucking up liquids, and that while drinking sirup the 

 tongue is protruded for half an inch or so and worked rapidly back- 

 ward and forward. 



Certainly there can be no sucking in the proper meaning of the word, 

 since no vacuum can be formed at the back of the tongue, and liquids 

 probably pass through the tubular portion by capillary attraction. 



It seems probable, as stated by Professor Newton, that the chief use 

 of the tongue is to capture small insects, and the size of the salivary 

 glands suggests that the tongue may be covered with a viscous secre- 

 tion to which minute insects would adhere, and thrust into crevices 

 ! beyond the reach of the beak. 



