AXSERES 465 



here and there ; their diameter is about an inch. The 

 bronchial rings which cover them have largely lost their 

 individuality, and form an irregular network of partly 

 cartilaginous and partly osseous bars. 



The males ('? as to females) of Cijgnus ferns and C. 

 Bewicki at any rate show less marked traces of the same 

 peculiarity. 



In the former there is a distinct fusiform dilatation, but 

 further down the bronchi than in C. buccinator, between 

 the rings of which there is some slight formation of 

 anastomoses. In C. Bewicki both features are still less 

 marked. 



Cygnus olor, C. atratus, C. nigricollis, and C. coscoroba 

 have no trace of this remarkable structure. I have examined 

 males of all and females of two. 



As to the geese, Bernicla canadensis, Anser indicus, and 

 Gereopsis Novce Hollandia (and doubtless many others) have 

 a syrinx without the anatine bulbus. It is present in 

 Plectropterus (gambensis, Ruppeli, niger) and Sarcidiornis, 

 and present, though small and solid, in Chenalopex jubata. 

 It is fenestrated in Plectropterus, not so in Sarcidiornis. 



Dendrocijgna appears to illustrate the commencement of 

 the syringeal enlargement. In the male of D. arcuata the 

 last twelve tracheal rings are widened and enclose a spacious 

 chamber about twice the diameter of the rest of the trachea. 

 The intrinsic muscles are attached to the beginning of this 

 thin-walled box. In the female there is an indication of 

 this in the fact that eleven of the tracheal rings in front of 

 the last three are imperfect posteriorly, being closed by 

 membrane. The intrinsic muscles also are attached opposite 

 to the commencement of this modified region of the trachea. 



In D. autumnalis there is the same box, which is 

 strengthened posteriorly by a strong bony bar. The wind- 

 pipe of the female has no such modification as has been 

 described above in D. arcuata. 



It is possible that this single enlargement in Dendrocijgna 

 is the beginning of both the tracheal swelling and the 

 syringeal bulbus in Mergus, &c. 



H H 



