198 



OHAS. B. WILSON. 



Pig. 74. — Longitudinal vertical section of pilidium; apical plate fully 

 developed with apical muscle attached ; aboral ectoderm much flattened and 

 perfectly transparent ; oral ectoderm thicker, more opaque, and beginning to 

 invaginate anteriorly; micromesencytes scattered over the inner surface of 

 both ectoderm and entoderm. 1 and 7. 



Fig. 75. — Transverse section of lappet ; three rows of cells bearing long 

 cilia ; locomotor muscles. 3 and one twelfth oil immersion. 



Fig. 76. — Longitudinal section of apical plate, showing arrangement of 

 flagella in bunches and the connection of the muscle-fibres. 3 and one 

 twelfth oil immersion. 



Fig. 77. — Longitudinal vertical section through the lappet, the oesophagus 

 wall, and the stomach. The locomotor muscle band {lom.) is here seen to be 

 continuous with the circumoral muscle {com.). 3 and one twelfth oil 

 immersion. 



Fig. 78. — Longitudinal vertical section of the lappet through the wall cells 

 of the cilia rows, with a portion of the locomotor muscle band and tiie mesen- 

 chyme cells forming the radial muscles of the lappets. 3 and one twelfth oil 

 immersion. 



Fig. 79. — Longitudinal vertical section as in Fig. 77, showing the locomotor 

 muscle band composed of cells and fibres. 3 and one twelfth oil immersion. 



Fig. 80.— Longitudinal vertical section of stomach, showing ordinary ento- 

 derm and gland cells. 3 and one twelfth oil immersion. 



Fig. 81. — Same as Fig. 77, but showing more plainly the row of mesen- 

 chyme cells which form the radial lappet muscles. 



Fig. 82. — Longitudinal horizontal section just above the mouth, showing 

 the two anterior invaginations with mesoderm attached ; the walls of the oeso- 

 phagus with a central groove posteriorly for the food particles. 3 and 8 ; 

 tube drawn 60 mm. 



