50 FEMALE UROGENITAL ORGANS OF PERAMELES, 



In a previous paper (3, p. 389) I gave a short account of the 

 histolog}'^ of the normal uterus, and need only add here a few 

 remarks on the uterine musculature. This is essentially com- 

 posed of circularly running non-striate fibres. Along the attach- 

 ment of the ligamentum latum, oblique strands of fibres are 

 found extending in from the musculature of the ligament, while 

 in the connecting bridge between the bodies of the uteri similar 

 oblique strands pass between the circular muscle layers. In 

 both places, together with these oblique strands, there occur 

 irregularly distributed bundles of longitudinal Hbres, but these do 

 not extend round the dorsal and ventral surfaces of the uteri to 

 form a continuous layer of longitudinal muscles. 



Both Owen (1), and Brass (4) who describes the histology of 

 the uterus of Phascolomys ivombat, agree in stating that the 

 musculature of the uterus consist of an outer longitudinal and an 

 inner circular layer of fibres. In representatives of the following 

 genera, Petroyale, Acrohates, Petaurus, .Sminthopsis, /'eragale, 

 Dasyurus, Macropus, Myrmecohius, Tarsipes and Phascolomys, I 

 find, however, that the uterine musculature has the same simple 

 character as in Permneles; in all these forms the musculature is 

 essentially a circular one. Even in Phascolomys where the 

 bundles of longitudinal fibres are strongly developed on the 

 lateral and mesial surfaces of the uteri, they do not form a con- 

 tinuous layer all round the uterus. 



This fact that the musculature of the uterus in Marsupials is 

 esentially a circular one is a point of some little interest and has 

 not, so far as I am aware, been emphasised. Sobotta (7) has 

 shown that the proper fundamental musculature of the uterus is 

 the circular layer which primitively forms the muscular invest- 

 ment of Miiller's duct. The layer of longitudinal muscles and 

 the intermediate layer carrying blood vessels are only differentiated 

 later and reach a very varying degree of development in different 

 mammals. Where then, as in Marsupials, we find continuous 

 longitudinal and intermediate layers absent and the uterine mus- 

 culature essentially composed of cii^cularly running fibres, we can 

 only regard the condition as a primitive one and as a mark of 

 lowly organisation. 



