86 MR. F. E. BEDDARD OX THE 



.slightest kink in the ahmentary tube. The rest of tlie tube is 

 disposed in four parallel and transversely arranged lines, which on 

 further examination are seen to form a. spiral and which end in 

 a longitudinal section of gut running to the cloaca. I cannot 

 distinguish in this a jejunal from an ileic region. It is interesting 

 to compare with this " degeneration " of the intestinal tract in 

 the fruit-eating Pigeons the coiresponding alterations met with 

 in the fruit-eating Passerine yEluro&dus. In that biixl there is 

 a vestige left of the duodenal loop, to the extremity of which the 

 pancreas reaches. Indeed, the rest of the gut has retained, 

 though in a reduced condition, the two recognisable divisions, of 

 which the ileum is represented, as in the primitive Picopasseres, 

 by f\ straight tract parallel with and connected by the usual 

 membrane to the duodenal loop. 



§ Some General Considerations. 



The new facts which have been described in the foregoing 

 pages give rise to certain reflections upon the affinities which 

 they appear to indicate between different families of birds and 

 upon the course pursued in the evolution of the gut of birds. 

 The facts, so far as they are known, do not appear to me to lead 

 to the establishment of a phylogenetic scheme, even of the 

 evolution of the gut only, so elaborate in the setting forth of 

 details as that which is drawn up by Dr. Mitchell as the result of 

 his own labours in this department of anatomy. ISTevei'theless, it 

 does seem possible to indicate certain stages in the evolution of 

 the intestine, and here and there are indications, already to some 

 extent considered, of affinities between different Avian families. 



§ The Primitive Form of the Intestine in Birds. 



It is obviously necessary, before considering the features which 

 are the most primitive in the Avian alimentaiy tract, to get a 

 clear notion of the essential differences which distinguish the 

 alimentary ti-act of Reptiles from that of Birds ; by this means we 

 shall evidently arrive at the essential resemblances. Dr. Mitchell 

 distinguishes the bird's intestine thus: — " It is distinguished from 

 the intestinal tract of reptiles chiefly by the fact that the three 

 divisions — the duodenum, Meckel's tract, and the rectum — are 

 sharply marked off" one from the other." These lines are written 

 of Palamedea, which that author regards "as representing closely 

 the ancestral type." It appears to me, however, that while 

 Palamedea is undoubtedly an ancient type, the definition used by 

 Dr. Mitchell is not a correct one. For, while in, at any rate, the 

 majority of Lizards known to me there is a very marked dis- 

 tinction between the small intestine and the large, the Crocodiles 

 show a further differentiation ; for they show a, very well-marked 

 duodenal loop as well. The divisions of the alimentary tract 

 therefore do not enable us to distinguish bet\veen Birds and 



