52 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANNIAE. 



Fig. 64. Similar section farther back. In the middle of the thickened ventral surface 

 of the caudal portion of the section is shown the proctodoeal involution. 



Fig. 65. Section through the plane of junction of the abdominal and anterior regions. 

 It passes through the angle of flexure. The ventral surfaces are seen to be united, the 

 flexure being a ventral one. Trophic ectoderm denotes the dorsal side of the embryo and 

 is indicated by dotted lines. The lower independent portion of the section passes through 

 the region of the primitive streak which is now much reduced from the condition shown 

 in Fig. 51. It now resembles the original condition seen in Figs. 42 and 47. In fact having 

 nearly served its purpose it is on the way to disappear. 



