266 MULLEEIAN AND WOLFFIAN DUCTS. 



the female united with the segmental duct. The anterior 

 end of the Wolffian duct is very much smaller than the oviduct 

 adjoining it, and as the reverse holds good in the male, an easy 

 method is afforded of distinguishing the two sexes even at 

 the earliest period of the formation of the Wolffian duct. 



Hitherto merely the general features of the development of 

 the oviduct and Wolffian duct have been alluded to, but a 

 careful inspection of any good series of sections, shewing the 

 junction of these two ducts, brings to light some features worth 

 noticing in the formation of the oviduct. It might have been 

 anticipated that, where the two ducts unite behind as the 

 segmental duct, their lumens would have nearly the same dia- 

 meter, but normally this appears to be far from the case. 



To illustrate the formation of the oviduct I have represented 

 a series of sections through a junction in an embryo in which 

 the splitting into two ducts had only just commenced (PI. XX. 

 fig. 1), but I have found that the features of this series of 

 sections are exactly reproduced in other series in which the 

 splitting has extended as far back as the end of the small 

 intestine. In the series represented (PL XX.) 1 A is the fore- 

 most section, and 1 D the hindermost. In 1 A the oviduct (o d) 

 is as large or slightly larger than the Wolffian duct (w.d), 

 and in the section in front of this (which I have not re- 

 presented) was considerably the larger of the two ducts. In 

 1 B the oviduct has become markedly smaller, but there is no 

 indication of its lumen becoming united with that of the Wolffian 

 duct — the two ducts, though in contact, are distinctly separate. 

 In IC the walls of the two ducts have fused, and the oviduct 

 appears merely as a ridge on the under surface of the Wolffian 

 duct, and its lumen, though extremely minute, shews no sign 

 of becoming one with that of the Wolffian duct. Finally, in 

 ID the oviduct can merely be recognised as a thickening on 

 the under side of the segmental duct, as we must now call the 

 single duct, but a slight bulging downwards of the lumen of 

 the segmental duct appears to indicate that the lumens of the 

 two ducts may perhaps have actually united. But of this I could 

 not be by any means certain, and it seems quite possible that the 

 lumen of the oviduct never does open into that of the seg- 

 mental duct. 



