ALIMEXTARY TRACT OF CERTAIN BIRDS. 51 



CasitcD'iitsimd Dromceus, but I find his description defective in one 

 particular and the illustration which he gives of Casucunits 

 correspondingly inaccurate. It would be inferred from that 

 figure * that the gut lay in a single line without any attachment 

 between the ileum and duodenum ; that — to use Dr. Mitchell's 

 own term — there was no vestige of a supraduodenal loop. The 

 existence of this attachment is indicated by him in other cases by 

 a cut blood-vessel ; there is no such " short circuit " represented in 

 his figure of the Cassowary. Nevertheless, two species of Casso- 

 wary which I have dissected, viz. C. australis and G. tvestermanni^ 

 show such a connection, which is not, however, associated with 

 the formation of an ileic loop distinguishable from the jejunum. 



Nor can I agree with Dr. Mitchell's figure of Apteryx, unless, 

 indeed, the species examined by him (^A. manteMl) differs from 

 that exaiiiined by myself {A. australis). For I find in the latter 

 bird no definite ileic loop, but only an attachment by mesentery 

 of the latter part of the ileum to the duodenum. The bird, in 

 fact, exactly resembles Gasuarius, Struthio, and the Gallinaceous 

 birds in this particular. 



In Rhea aniericana the -intestine is formed upon a plan which 

 may be interpreted in one of two ways — one of which is certainly 

 not " archicentric " in the sense in which Dr. Mitchell uses the 

 word, and the other interpretation hardly justifies the use of the 

 word " archicentric." Since, in various other points of structure 

 (e. g. less degeneration of wing, syrinx), Rhea is much less 

 "Struthious" than Gastoarms, it might be expected that the 

 intestinal tract also would be more like that of Carinate birds. 

 The accompanying figure (text-fig. 9, p. 52) shows the course of the 

 intestine in a female example of Rhea americana, and may be com- 

 pared with the figure drawn by Dr. Mitchell t from the intestinal 

 ti-act of the same species, with which I do not find myself able to 

 agree entirely. Dr. Mitchell, however, is perfectly right in dis- 

 tinguishing two loops only in the small intestine, viz., the duodenal 

 and another which may or may not be the ileic loop of other birds, 

 or " supraduodenal," as it is termed by him. 



This latter loop is wider as well as longer than the duodenal 

 loop, and it lies parallel with it as does the ileic loop (nearly 

 always) in other birds, and is connected with the duodenal loop by 

 the usual ileo-duodenal ligament, which is long and extends nearly 

 to the end of the duodenal loop, while it is attaclied along more 

 than half of the length of the loop now under consideration. So 

 far the facts point towards the interpretation of this loop of the 

 small intestine in Rhea as being the homologue of the ileic loop 

 of other birds. If this interpretation be correct, then the jejunal 

 region or loop will be practically absent and reduced merely to the 

 small, tract just where the lower limb of the duodenal loop bends 

 round to join the lower limb of the (for the moment) alleged ileic 

 loop. There is, I think, nothing intrinsically absurd in this 



* P. Z. S. 1896, p. 140, fig. 3. 



t Trails. Linn. Soc. t. c. p. 183, fig. 3. 



4* 



