82 
MORGAN. 
PLATE IV. 
Fig. 23-34: Stage III. Fig. 35-40: Stage IV. 
Fic. 23. (Stage III.) Surface view of posterior plate. 
24. Surface view of small circular band. 
25. Surface view of larger circular band. 
26. Cross-section of middle of body. 
27. Cross-section of ectodermal tube leading to mouth. 
28 aand 6. Cross-section of oesophagus. 
29. Cross-section of lateral wall of body. 
30. Cross-section of third body-cavity. 
31. Cross-section of second body-cavity. 
32. Surface view from side of first body-cavity and proboscis vesicle. 
32 A. Section through last. See vertical line in 32. 
33 4-F. Section through Fig. 32. See horizontal lines in 32. 
34. Surface view (from section) of wall of proboscis vesicle. 
35. (Stage IV.) Cross-section of lateral wall of body. 
36. Cross-section of tentacle. 
37- Longit. section of apical plate. 
38. Cross-section of anterior wall of stomach. 
34. Surface view of wall of third body-cavity. 
40. Cross-section of proboscis wall and first body-cavity. 
41. (Between Stage V and Stage VI.) Longit. section of Tornaria. 
42. Earliest stage of collar-pores. Longit. section. 
43. Two mesenchyme cells of blastocoel. 
44 a and 4, Surface view and optical section of eye. 
45. Actual section of eyes and apical plate. 
46. (Older) surface view of apical plate. 
47. Longit. section of wall of proboscis. 
48. Cross-section of body proper, (older). 
49. Beginning of dorsal nervous system. 
