50 ME. F. E. BEDDARD ON THE 



are represented as being almost identical. In particular, Dr. 

 Mitchell does not always distingnisli between fixed loops, definitely 

 formed by a narrow mesentery, and the iri-egular folds into 

 which any mobile coil of the intestine may fall when disposed on 

 the dissecting-board in Dr. Mitchell's fashion. I shall recur to 

 definite instances in the course of this communication. 



1 shall now -proceed to deal with the intestinal tract in a 

 number of species of birds. 



§ Description of the Intestinal Tract in various 

 G^-oujis of Birds. 



. On opening the abdominal wall of most birds the intestine is 

 usually seen to form a rather compacted mass, such as is figured, 

 for example, by Dr. Gadow in most of the plates which illustrate 

 his original memoir upon the intestinal tract in birds. This 

 mass consists of parallel or concentrically arranged loops of intes- 

 tine, and in the higher birds, such as a Heron, a Duck, or Stork, is 

 very characteristic. This appearance of the gut distinguishes it 

 at once from the Mammalian or Reptilian gut, where the intes- 

 tine lies laxly within the abdominal cavity. 



This also is the case with all the Struthious birds, whose intes- 

 tinal tract at the first glance recalls that of a Mammal. A little 

 disturbance of the apparently compact intestinal mass of some 

 other birds, as, for instance, the Eagles and Hawks, shows that 

 here, too, the intestinal tract is not really much welded together, 

 but simply lies pushed close coil to coil, owing to the limited space 

 in which it has to be stowed away. In other cases, however, it 

 can be easily ascertained by the gentle pulling apart of the 

 intestinal coils that the gut is disposed in tightly fixed loops. 



This is the case, for instance, with Ducks, Storks, Penguins, 

 and a variety of other genera and families. Inasmuch as the 

 lax condition of the small intestine in such a bird as an Ostrich 

 recalls that of the Mammalia and Reptiles, and is really like the 

 intestinal tract in those Vertebrates, it is to be assumed that this 

 condition of the bird's gut is the more piimitive condition and 

 that the specialisation into definitely fixed concentrically or 

 parallel arranged loops, whether narrower or wider, is an index of 

 the higher position of the bird in the series. I shall commence the 

 following survey of such new facts as I have to add to the matter 

 in hand by dealing with the more primitive groups of birds first. 

 Indeed, I have not attempted in this paj)er to map accurately the 

 coils in several families of birds where they axe very complicated, 

 such as the Stork tribe ; for I am not satisfied as to the relationship 

 of the coils in these birds to the more simple intestine of lower 

 forms. It is almost entirely with the latter that I deal in the 

 present communication to the Society. 



Of the RATiTiE I have examined all the living genera. I fully 

 agree with Dr. Mitchell as to the basal position in this group of 



