1900.] F. Finn — Structure and Function of the Tracheal Bulb. 147 



IX. — Notes on the Structure and Function of the Tracheal Bulb in male 

 Anatidas. — By F. Finn, B.A., F.Z.S., Deputy Superintendent of the 

 Indian Hits item. 



[Received 30fch May ; Read 6th Jane, 1900.] 



The peculiar bony, or bony and membranous, bulbs found at the 

 base of the trachea in so many males of the duck tribe, are well known 

 to be confined to individuals of that family and sex alone. But, well 

 known as the Anatidse are or should be, from the fact that so many 

 species are shot for food or kept in captivity, thus making specimens 

 easily available for dissection, this structure of the trachea does not 

 appear to have been recorded in some even of the best known species, 

 nor does its functional importance ever appear to have been fully 

 realized. It is my purpose here to note briefly some specific peculiarities 

 in the form of the organ which seem to have escaped the notice of 

 naturalists, and to conclude with some observations on its presumable 

 use. 



Nettopus coromandelianus. 



In writing a popular series of articles in the Asian newspaper 

 in 1898-99, destined for sportsmen who wished to identify the ducks 

 they shot, I was careful to note the structure of the trachea in each 

 species when I was able to give the information, in hopes of interesting 

 my readers in this point. Thus I mentioned that the male of the above 

 species was devoid of a tracheal bulb, a fact I had ascertained from my 

 own examination of the trachea of this bird. Dr. W. T. Blanford, in a 

 letter to me on the subject, has informed me that this observation is 

 new, and I am hence induced to record it here. I find, however, that 

 Sir E. Newton (Ibis, 1863, p. 459), says of Nettopus auritus, "Unlike 

 most other ducks, the trachea of the male in this species is of a very 

 simple form, there being scarcely any enlargement whatever at the 

 lower extremity." It is possible, therefore, that the absence of a 

 tracheal bulb may characterize the genus, as appears to be the case with 

 Erismatura, in which genus MacGillivray, presumably referring to 

 E. rubida, states that " There is no expansion or tympanum, as in other 

 ducks " (Orn. Biogr., vol. iv, 1838, p. 331, fide Beddard, Structure and 

 Classification of Birds, p. 464, footnote). Pallas certainly states (Zoog. 

 Ross. As., vol. ii, p. 285), that such a tympanum is absent in E. leuco- 

 cephala, a fact which I have been able personally to verify (see J.A.S.B., 

 vol. Ixvi, pt. 2, p. 527). It would, however, be rash to assume that 

 such deficiency of the tracheal bulb must necessarily apply to all the 

 species of these genera, since among the members of the genus 



