INTESTINAL TEACT OF 151RDS. 175 



this memoir represent the intestinal tracts of various birds as seen in preparations of 

 the kind described, and tlierefore illustrate the morphological conditions of the tracts. 

 In 1896 (26) I bad already a considerable material, and described and figured some of 

 the chief modifications of the common tyjic displayed in the groups of birds. Since 

 then I have been able to add largely to my material. I liave now examined many 

 bimdreds of birds, including a number of rare forms, and representing nc^arly all the 

 important groups of birds. Taking the System given by Dr. (ladow in Bi'onn's 'Thier- 

 Reich,' vol. vi. part ii. pp. 290-301, as one specially familiar to anatomists, I find that my 

 material includes, so far of course as living forms go, all the groups of llatites, and, of 

 Carinates, all the Orders, all the Suborders except Mesitcs, and all the Pamilies except 

 Mesitidoe, Galbulidse, and some Passerine families. For materials I am indebted to the 

 authorities of the National Collection, who have allowed me to examine a number of 

 s])irit-specimens, to sevei'al private persons, iucluding in particular Mr. C. Hose of 

 Borneo through Mr. Beddard, but above all to the Zoological Society of London. 

 Isearly all the work was done at the Prosectorium on materials from the Gai'dens or 

 sent to the Prosector. To my friend the Prosector, Mr. Beddard, F.R.S., I am deeply 

 indebted both for materials and assistance. To Prof. Howes, E.ll.S., I am indebted for 

 many valuable references to literature, and I have had the advantage of discussing the 

 nom.enclature of charactei's with Pi-of. Ray Lankester, E.R.S. 



The Tract in Falamkuka cohnvta as an Aucuecentkic Type. 



It is convenient to describe the conditions of the intestinal tract in one form in some 

 detail so as to provide a standard for comptirison and to avoid unnecessary repetition. 

 In a former paper (26. p. 138, fig. 2) I took the condition in an embryo of an Argus 

 Pheasant, about thirty days old, as a starting-point ; here, for various reasons which will 

 appear later, I begin with the condition in the Horned Screamer, Palamedea corimta 

 (fig. 1). When unfolded, in the fashion already described, the intestinal tract is seen 

 to present three main portions between the pyloric cut end {p.) and the cloacal cut 

 extremity (cZ.). The first division from^j. to the point w^iere, ^i]).v., the cut portal vein 

 is represented consists of a long, narrow, and closed loop ; this is the duodenal loop of 

 Cuvier : it contains the pancreas between its ascending and descending limbs, and 

 receives the ducts of the pancreas and liver. It always in the undisturbed condition 

 lies bent backwards towards the cloaca, ventrad of all the other loops, and is therefore; 

 the first portion of the gut to be seen when the abdomen is opened from the ventral 

 surface in the usual fashion. Its ascendiu"- and descending limbs are held together bv 

 a narrow outgrowth of the mesentery. The mesentery, after leaving the duodenum, 

 expands into a large, nearly circular fold, at the circumference of which, from the 

 end of the duodenum to c.c, the point of insertion of the cjBca, is suspended the great 

 portion of the intestine. About the middle of this portion is situated Meckel's Diverti- 

 culum (m.), which is well known to be a relic of the embryonic stalk of the yolk-sac 

 {cf. 26. tig. 2). This portion I name Meckel's Tract, as it carries Meckel's diverticulum. 

 In PaZ«??2^rf^«itpi'esents a number of minor, simple corrugations, but in more specialized 

 forms the loops present extremely definite and well-marked types of divergence from 



28* 



