5t2 



EL A S MO BRA NCHII. 



mental duct (alter the loss of its anterior section, and the part split 

 off from its ventral side) forms the Wolffian duct. The process of 



-/np 



ch 



Si 



> 



Fig. a88. I)i\ttKVMM\Jic hepkkskk- 



TATION or A TllANSVEESE SKCl'lON 01' A 

 ScYIiLIUM EMBRYO ILLUSTBATING THE FOR- 

 MATION OF THE Wolffian and Mullerian 



DUCTS BY THE LONGITUDINAL SPLITTING OF 

 THE SEGMENTAL DUCT. 



mc. medullary canal; mp. muscle- 

 plate; ch. notocbord; ao. aoita; cav. 

 cardinal vein; &t. segmental tube. On 

 the left side the section passes throuRh 

 the opening of a segmental tube into the 

 body cavity. On the right this opening 

 is represented by dotted lines, and the 

 opening of the segmental tube into the 

 Wolfiian duct has been cut through; w.d. 

 Wolffian duct: m.d. Mullerian duct. The 

 section is taken through the point where 

 the segmental duct and Wolffian duct 

 have just become separate; gr. the ger- 

 minal rilge with the thickened germinal 

 epithelium; I. liver; i. intestine with 

 spiral valve. 



trcb 



Fig. 389. Fouk sections 

 through the anterior part 

 of the segmental duct of a 

 F!::male embryo of Scylj>ium 

 canicula. 



The figure shews how the 

 segmental duct becomes split 

 iuto the Wolffian or meso- 

 nephric duct above, and Miil- 

 lerian duct or oviduct below. 



wd. Wolffian or meso- 

 nephric duct ; od. Miillerian 

 duct or oviduct ; sd. segmen- 

 tal duct. 



formation of these ducts in the male differs from that in the female 

 chiefly in the fact of the anterior undivided part of the segmental 

 duct, which forms the front end of the Miillerian duct, being shorter, 

 and in the column of cells with which it is continuous being from 

 the first incomplete. 



The segmental tubes of the mesonephros undergo further im- 

 portant changes. The vesicle at the termination of each peri- 

 toneal funnel sends a bud forwards towards the preceding tubulus, 



