Development of the Third Day 219 



twisted and convoluted, the Wolffian body 

 becomes greatly enlarged, and causes the 

 marked ridge that projects into the body- 

 cavity on each side of the median line (Fig. 71). 

 Owing to the above-described changes that 



Fig. 71. — Transverse section through the dorsal 

 region of an embryo of 68 hours, a short distance 



ANTERIOR TO THAT REPRESENTED IN FiG. 70. (After 

 Duval.) 



Cam^ amnioric cavity. VOM and ?>/, vitelline veins. Other 

 lettering as in Fig. 70. 



have taken place in the mesoblast of the 

 trunk, the position of the Wolffian duct is 

 changed, during this day. Instead of lying 

 close under the ectoblast as it did during the 

 second day (Fig. 54, CIV), it shifts its position 

 downwards until it lies near the middle of the 



