662 



DR. P. CHALMERS MITCHELL ON THE 



duodenal loop, and then two supi^a-caecal kinks. This region 

 supplies no definite information which might help to place 

 Balceniceps inside the Legion. 



In the Legion the colic cteca are much reduced and apparently 

 practically functionless except in the Anseriformes, in most of 

 which they are very large and functional. Although reduced in 

 the Steganopods, they are rather less so than in the Herons 

 and Storks and occasionally contain ftecal matter. I think the 

 presence in Balceniceps of a single C£ecum, by no means so large 

 as either of those in the Anseriformes, but definitely functional, 

 communicating with the hind-gut and containing feecal matter, 

 may be taken to be established. The presence of one cfecum, 

 instead of the normal pair, associates Balceniceps with the Herons. 

 I should be disposed to guess that the loss of one ceecum of the 

 pair had taken place whilst botli were functional, as there seems 

 no particular reason why one of two vestigial organs should be 

 suppressed, except as an occasional abnormality, and that the 

 condition in the Herons, where there is a single functionless 

 caecum, is secondary to that in Balceniceps. 



The characters of the large intestine in Birds generally are not 

 sufiiciently differentiated to afford much information of systematic 

 value. There seems to have been a general tendency to the 

 reduction of this area to an extremely short and straight course 

 from the cseca to the cloaca, a tendency which has been inde- 

 pendently followed by the higher members of a large number of 

 groups. Balcenicejys has a relatively long and capacious large 

 intestine, and in so far has remained in a rather more primitive 

 condition than most of the members of the Pelargomorphine 

 Legion. 



To sum up, the characters of the intestinal tract of Balceniceps 

 are those of the Pelargomorphine Legion, and such specialization 

 as it displays associates it with Ardeine birds rather than with 

 Ciconine birds. 



In a communication to this Society, Dr. Beddard (5) has 

 made some additions to or corrections of my observations, 

 particularly with regard to the presence of a specialized supra- 

 duodenal loop in birds in which I did not record it, which are the 

 more valuable as my work stretched over a number of years, as 

 material was available, and it was only in its course that I began 

 to recognize the significance of the various points and what had 

 specially to be looked for. Dr. Beddard also on several grounds 

 throws doubt on the value of my mode of displaying and com- 

 paring the intestinal tract patterns. These grounds are due to 

 misapprehension. He thinks that my method of figuring the 

 tract gives " an appearance of simplicity that is misleading, with 

 the result that birds which are separated by marked characters 

 are represented as being almost identical." Certainly the patterns 

 (even if correct) do not in every case afford enough information 

 to place clearly, or to separate clearly cases where the patterns 

 are very simple. I was rather careful to insist on this point in 



