188(j.] ANATOMY OF CHAUNA CHAVARIA. 1/9 



former group, since the lobes of the liver are not shut off by septa 

 from the space which lies between the horizontal membrane and the 

 ventral abdominal walls. In the Cranes, as in the Struthious birds, 

 the lobes of the liver are enclosed in separate compartments distinct 

 from that underlying the horizontal membrane (c/". P. Z. S. 1885, 

 p. 836). 



There are other points in which Chnuna apf)roaches the Storks. 

 In the paper already referred tr, Weldon has drawn attention to a 

 peculiarity in the air-sacs of the Storks which appears to be 

 characteristic of this group, and is at any rate not to be found in 

 the Ducks. The prsebronchial air-sacs (in the Storks and Phceni- 

 copterus) are divided by a complicated arrangement of transverse 

 septa into smaller chambers. 



In Chauna chavaria this subdivision of the prsebronchial air-sacs 

 is very much more marked, and the subbronchial air-sacs, which in the 

 Storks and many other birds are fused into a single cavity, are in the 

 same way divided up into an immense number of extremely small 

 chambers, so that the whole air-sac presents the appearance of a 

 crowd of air-bubbles closely pressed together of various sizes. It 

 was quite impossible on this account to distinguish the prsebronchial 

 from the postbranchial sacs, that is to say at the points where they 

 come into contact. 



The prolongations of the subbronchial air-sacs into the axilla and 

 into the space between the two pectoral muscles were similarly sub- 

 divided by innumerable septa. 



There appeared to be nothing remarkable in the disposition of the 

 abdominal air-sacs, and there were no indications of any subdivision 

 of these chambers ; the anterior intermediate air-sac communicates 

 with the bronchus by two apertures placed side by side and at some 

 distance from each other near the anterior end of the chamber ; 

 in the posterior intermediate sac, which was considerably the larger 

 of the two, there was only a single pulmonary orifice. 



The abdominal air-sacs present the usual character — the right 

 being considerably larger than the left. 



It appears to be the general rule that the thoracico-abdominal air- 

 sacs are not divided up in the way that the cervical air-sacs are in 

 Chauna and in the Storks ; but I have met with occasional variations 

 in the structure of their air-sacs in some few out of the numerous 

 birds which I have had the opportunity of dissecting. In Steatornis 

 I have already (supra, p. 151) called attention to the fact that 

 the posterior intermediate air-sac was either completely separated 

 into two distinct compartments or had indications of such a division ; 

 in a specimen of Strix jlammea there was a similar division of the 

 posterior air-sac, at least on one side of the body. The third instance 

 is Platalea leucorodia ; in a specimen of this bird, on both sides of the 

 body there were three " intermediate" air-sacs, the third being very 

 small and interpolated between the anterior and posterior intermediate 

 sacs. This may of course be an abnormality ' ; but the air-sacs of 

 birds differ so little that any fact seems worth recording ; and the 

 ' A second specimen had the noruial number of abdominal air-sacs. 



