ANATOMY OF THE SHOE-BILL. 



653 



with a slight tendency to be aiTanged in longitudinal bands, but 

 there is no indication of separation into a glandular proventri- 

 culus and a muscular gizzard, and no trace of aggregation into 

 specialized patches or areas. 



Text- fig. 121. 



A 



Stomach of Balcenice'ps. 



The distal end of the stomach and the pyloric chamber have been laid open to show 

 the constriction separating the general cavity from the cavity of the pjloric 

 chamber and the minute aperture, A, into D, the duodenum. 



We have to recognize in the first place that the absence of 

 distinction between proventriculus and gizzard gives no clue to 

 the position of Balcenicejys in the assemblage of Pelargo-Colym- 

 biform birds. F. S. Leuckart (23) discussed this formation in 

 1841, citing the earlier authors, such as Blasius and Cuvier, who 

 had called attention to it, described it in a number of birds and 

 associated it with diet. It is tempting to associate such an 

 undifferentiated condition with a primitive structure, but I do 

 not think that such a view is tenable. At one time I myself 

 thought that it might be possible to derive information useful for 

 systematic purposes from the condition of the stomach, and I 

 examined and made drawings of the organ in a large number of 

 birds. But throughout the group, fi'om Divers to Eagles, the 

 extent to which gizzard may be separated fi'om proventriculus by 

 external or internal configuration, by specialization of muscle and 

 tendon, or by aggregation of glandular areas, varies so irregularly 

 as to suggest adaptation to habit rather than genetic tendency. 

 The typical fish-eaters on the whole have a bag-like sac, weakly 

 muscular and diffusely glandular ; those that live more on flesh 



