1894.] VISCERAL AIS^ATOMY OF ORNITHOBHYXCHUS. 717 



ceivably be a variable structure. The animal, after bavingbasu 

 skinned, was carefully opened to the left of the middle line so as 

 not to interfere with any structures which might be there. I 

 found i)i the middle ventral line a fold of thin membrane depending 

 from ike parietes into the hodij -cavity. This fold was crumpled up, 

 but could be readily extended and was then seen to be fully a 

 quarter of an inch in diameter. This fold ivas attached posteriorly 

 to the bladder, and anteriorly became continuous with the falciform 

 ligament of the liver. This fold must, I think, be regarded as the 

 remains of the primitive venti'al mesentery. I strongly suspect, 

 but have unfortunately an insufficient recollection of the facts to 

 confirm my suspicions, that a similar fold exists in Echidna. 

 That it should be anangious in the one case and bear a blood- 

 vessel in the other is interesting but not unintelligible. To quote 

 one out of many analogous instances, certain of the mesenteries 

 supporting the caecum in the Lemurs may or may not have blood- 

 vessels \ 



The Alimentary viscera have been described by so many authors, 

 including Home ", Meckel ', and Owen ^, that I can limit myself 

 to a very few remarks. The expression " de grandeur moyenne," 

 applied by Meckel to the stomach", and repeated by Sir E. 

 Owen '', is less applicable to the stomach which I examined than 

 the expression used by the translators of Meckel, viz. " extre- 

 mement petit." In Meckel's original figui'e, copied by Owen in 

 the ' Comparative Anatomy,' the dimensions are too great. I 

 found the greatest diameter of the stomach to be Ig inch (exactly 

 Sir B. Home's measurement), as against 5 feet 4 inches total 

 length of ahmentary canal. 



When the viscera were fully displayed by cutting and reflecting 

 the abdominal parietes, the omentum was seen to extend right 

 back to the pelvic region. It is attached to about the last four 

 inches of the large intestine. 



The slender caecum is about one inch long and is about 11 

 inches from the cloaca. The valvulse conniventes of the small 

 intestine have been figured by Meckel ; but as his figures are a 

 little rough and do not quite do justice to the structures, I have 

 thought it worth while to have the accompanying drawing 

 prepared (fig. 1, p. 718). At about the distance of one foot from 

 the caecum the valvulae conniventes come to an end. Their termi- 

 nation is rather more abrupt than I should have supposed from 



1 Beddard, " Additional Notes upon Hapalemur griseus" P. Z. S. 1891, p. 451 

 et seqq. 



^ " A Description of the Anatomy of the Omithorhyiichus paradoxus,^' Phil. 

 Trans. 1802, p. 67. 



' Ornithorhynchi paradoxi descriptio anatomica. 



* " On the Young of the Ornithorhynchus paradoxus, Blum.," Tr. Z. S. vol. i. 

 p. 221 



» ' Traits g^nSral d'Anatomie Compar^e,' Trad. Fr. (Paris, 1838), vol. viii. 

 p. 539. 



* ' Comparative Anatomy of Vertebrates ' (London, 1868), vol. iii. p. 410. 



