78 MR. F. E. BKDDARI) OX THE 



In Tooth, it should be added, there was a distinct snpracjpcai 

 kink. 



I have dissected two examples of Sterna fiuviatilis which agree 

 absolutely in the characters of their gut. This genus — also like 

 Larus — is very definitely like the Limicolous birds. The pancreas, 

 as in those birds, extends back to the end of the duodenal loop. 

 The ileic loop is wide and of about the same length as the duo- 

 denal and, finally, the ileo-duodenal ligament is extensive and 

 reaches nearly to the end of the ileic loop in the one case, and for 

 more than halfway along the duodenum in the other. The 

 jejunum lies in a rather short spiral of not more than three 

 circles ; the coils of the spiral, however, are not so fixed as in 

 Recurvirostra, they can be pulled apart and ari'anged in about 

 three loops. This state of afl'airs has been figured by Dr. Mitchell 

 for Sterna hirundo, and his figui'e would fit perfectly the con- 

 ditions which I found to characterise Sterna Jluviatilis. There is 

 also a supracaecal kink. 



The Auks are associated by some with the Gulls*, but by 

 others they are regarded as forming a distinct assemblage t or are 

 associated with the Grebes and Divers into one group Pygopodes J. 

 An examination of the intestinal tract of Fratercula arctica, (text- 

 fig. 26) leads me to reject the former view and to hesitate between 

 one or other of the two latter classificatory schemes. At the same 

 time, it must be added that there is room for divergence of opinion 

 in the interpretation of certain of the loops, as will be seen from 

 the following account, in which I am unable wholly to confirm 

 Dr. Mitchell's account. The duodenal loop is not in any way 

 remarkable and quite unfolded. The pancreas extends nearly, 

 or in one specimen quite, to its end. Thereafter follow two loops, 

 which belong to the middle (jejunal) region of the gut. These 

 are set more or less at right angles to each other ; but the 

 direction of the loop is, as I think, of less importance than the 

 fact that there are two of them (and two only), which are roughly 

 equal in size and very distinct. 



Moreover, these two loops are interconnected by mesenteries. 

 It is obvious that we have here a close resemblance to the Grebes, 

 Tachyhaptes and Podiceps §, and to those birds only among those 

 whose anatomy in this i-espect is known. After these follows 

 a large ileic loop, which is difi"erent in sti'ucture to that of many 

 birds. Mitchell figures it as a simple wide loop. It is, however, 

 long and irregularly looped, and longer than the duodenal loop. 

 It appeared to me tha.t it ended in two prolonga.tions at its blind 

 end, in which case there is an obvious comparison possible with 

 the ileic loop in Podiceps cristatus ||, which is loosely folded at its 

 blind extremity. The small intestine before the casca is thrown 

 into another loop, which Dr. Mitchell has duly noted and has 



* U.ff., Mitchell, loc. cit. 



t ^.g., Beddard, 'The Stractuve and Classification of Birds': London, 1898. 



X -B. q-. Vertebrate List Zool. Soc. Lond. 1896. 



§ See" below, p. 81. || See p. 81. 



