214 TORREY 



TEXT-FIGURE 8. 



A, optical section of a living three-day trochophore. ap, apical plate ; ct, cili- 

 ated tract between the stomach and the intestine ; ex, excretory cells ; pa, para- 

 troch ; pr, prototroch ; vc, ventral ciliated region. B, view of the body wall of 

 a living trochophore. gp, green pigment ; gl, glands ; gr, granules. C, surface 

 view of the stomach wall (living), greatly magnified. D, section of the same. £, 

 optical transverse section of a stage of over 140 cells. The coelomesoblast cells, M, 

 are about to bud off two small entoblast cells. In this and the following figure the 

 ectomesoblast cells are stippled and the coelomesoblast cells are outlined with heavy 

 lines, emr, ectomesoblast right, arising from the c quadrant ; eful, ectomesoblast 

 left, arising from the d quadrant ; emtn, ectomesoblast median, arising from the a 

 quadrant. E, optical section from dorsal side and at right angles to the prototroch 

 of a slightly older stage, e, entoblast cells budded off from the coelomesoblasts, 

 M ; le, lateral ectomesoblast cell ; p.st, protoplasmic strand running from the ento- 

 blast to the ectoblast. The prototrochal cells are indicated by diagonal lines. 



