1894.] VISCERAL A]S^ ATOMY OF OBXITHOEHTlfCHtTS . 719 



reading the current descriptions of the gut. Though they are not, 

 as Owen remarks, nearly so close together in the posterior as in 

 the anterior part of the gut, I could detect no oblique disposition 

 of the folds. The Peyer's patches are very sUghtly developed in 

 this animal ; I only found one about 2 feet from the caecum and a 

 second one just below the origin of the caecum. 



The spleen in the animal dissected by myself was not bifid as it 

 has been described. It was a flat band lying diagonally across the 

 body-cavity and looked almost exactly like a coil of intestine. 



§ Male Generative Organs. 



Meckel's figure of these organs, which is copied by Sir Richard 

 Owen, does not appear to me to be accurate in every particular. 

 The testis is of a loose texture and is enveloped in a tough mem- 

 brane which can be readily dissected off. This is continuous with a 

 sheet of mesentery which supports the anterior convoluted portion 

 of the sperm-duct. It is not, however, only attached to one side 

 and to only a portion of that, as shown in the drawing of Meckel, 

 but is disposed as in the accompanying drawing (fig. 2, p. 720), an 

 inspection of which will render a detailed description unnecessary. 

 The appearances presented are chiefly due to the fact that the 

 mesorchium is attached to the sperm-duct, not along a straight, 

 but a curved line. This brings about the formation of a pocket 

 which is faint comparable to a similar pocket which is usually 

 found between the ovary and the Fallopian tube in female Mam- 

 malia. The convoluted character of the sperm-duct is well 

 illustrated in Meckel's figure referred to. It could be readily 

 injected Avith coloured flmd. 



§ The Heart. 



The heart of Ornithorhynchus has been so recently described, Avith 

 a full account of the previous memoirs relating to the matter, by 

 Prof. Lankester \ that I need not trouble the Society with any 

 general description. There are, however, some new facts to record 

 concerning the right auriculo-ventricidar valve (fig. 3, p. 721). I 

 have thought it AAorth while to have a drawing prepared of one of 

 the two hearts in my possession, which differ from each other to 

 some extent. Prof. Lankester found in the hearts examined by 

 himself that the " septal flap " of the valve in the half of the collar 

 which borders the septal side of the ostium was either entirely 

 wanting or but shghtly represented by a small flap on the right 

 side. This statement was contrary to that of Gegenbaur, who 

 asserted the existence of a complete circular valve like that of 

 other Mammalia. It appeared to Prof. Lankester that the absence 

 or rudimentary character of the septal flap was of greater import- 



' 1 " On the Valves of the Heart of Ornithorhynchis, &c.," P. Z. S. 1882, 

 p. 549 ; and " On the Eight Cardiac Valve of Echidna and of Ornithorhynchus,' ' 

 P. Z. S. 1883, p. 8. 



