652 DR. p. CHALMERS MITCHELL ON THE 



agrees in structui-e with that organ in Herons and in Scopus, it 

 conforms not with a structure that is specially Ardeine, but with 

 one that is found in so many diiferent groups that Beddard 

 himself has spoken of it as the typical avian syrinx. Storks, as 

 he himself has shown, display a series of stages most conveniently 

 regarded as degenerations in difFei-ent degrees from the typical 

 avian syrinx. Balceniceps shows degeneration, if not complete 

 absence of the intrinsic muscles ; it has not degenerated so far as 

 most of the Stoi'ks, but the fact is that as there is no typical 

 ciconine and no typical ardeine syrinx, the condition in 

 Balceniceps aflfbrds no clue to its relationship with either of these 

 groups. 



Carotid Arteries. — The normal condition, present in a large 

 number of birds of difterent groups, and what development and 

 comparative anatomy would seem to indicate as the primitive 

 avian condition, is the presence of both right and left carotids, 

 separate and well developed. This is the condition usual in 

 Steganopods, Herons, Scopus and Storks. I was surprised there- 

 fore to find that only the light carotid was present in Balcvniceps^ 

 and although I searched carefully, I could find no trace of even a 

 degenerate left artery. I do not attach systematic importance to 

 the condition of the carotids, as this often varies within a Family. 

 In Botcmrus, for instance, the two carotids fuse very close to 

 their origin, and in another member of the Ardeidee [Ardetta) 

 the right carotid only is present. 



Alimentary Canal. 



The tongue is only a, vestige as in Storks, Scopus and Cancrotna, 

 whereas it is long in Herons. 



Stomach. — The stomach is a capacious, elongated, rather thick- 

 walled sac, extending posteriorly in the line of the oesophagus, 

 from which it is to be distinguished externally only by a gradual 

 increase of calibre. Distally it ends in a blunted angular point, 

 and just proximal of this it gives ofi', on the right side, a globular 

 chamber from which the duodenum arises (text-fig. 122, P, p. 657). 

 Externally theie is no trace of any specially tendinous ai-ea, and 

 no constriction to mark ofi" a proA^entriculus from a gizzard. The 

 interior of the stomach, including the chamber at the pyloric 

 end, is lined with a thin but Avell-maiked layer consisting of the 

 hardened seci'etion of the gastric glands. The cavity of the 

 stomach is distinctly marked off' from that of the oesophagus by 

 the corrugated edge of the membrane-like layer of secretion. The 

 general cavity is sharply marked off from that of the pyloric 

 chamber by a well-marked constriction (text-fig. 121). The 

 greater part of the interior of the larger chamber is marked by 

 longitudinal folds, but towards the posterior end these pass into 

 irregular corrugations which are continued into the pyloric 

 cavity. When the internal surface is scraped and the wall 

 squeezed, the large glandular apertures may be seen to be 

 distributed over the whole area of the stomach and pyloric cavity, 



