84 
MORGAN. 
PLATE V. 
Cross-section of nervous system. Same series with last. 
Surface view of small circular band. 
Second “stage” in development of collar-pores. 
Cross-section of collar. 
Cross-section of proboscis wall and body-cavity. 
Surface view of outer wall of first body-cavity. 
Cross-section of proboscis vesicle, efc. 
Surface view of oesophagus with gill-pouches. Lower part figure is 
anterior. 
Longit. section of proboscis vesicle, efc. 
Longit. section of body. Invagination of ectoderm for gill-slit and 
collar-pore. 
Longit. section of body. Opening of collar-pore into second body- 
cavity. 
Longit. section of body. Same series as last. 
Longit. section of body. Same series as last. 
Cross-section of nervous system. 
(Stage VII.) Longit. dorso-ventral section. 
Cross-section of nervous system. Older than Fig. 63. 
Cross-section of nervous system. Older than Fig. 65. 
