Plate VIII. 



Fig. 6. Epithelium from the "chimney", showing the numerous gland cells lying in the interstitial 



tissue. 385/j . 



— 2. Transverse section of one of the branching peripheral canals, showing the two lobes of 



high epithelium separated by a band of low epithelium. Cilia could not be observed. 

 The cells of the lobes are somewhat vacuolated, c. c. cavity of the canal, m. t. mesodermal 

 (muscular) tissue, ^""/i. 



— 3. Epithelium from the stomodgeal folds; showing different stages of the gland cells, -t's/j. 



— 4. Longitudinal section of the tentacle, showing the muscular core and the coUoblast layer. ^°°li . 



— 5. Section of the skin of the chimney cavity; showing the cilia and gland cells (eosinophilous 



grains). 3^5/j. 



— 6. Transverse section of a costa, from an embryo in Stage II. -t'Vi- 



— 7. Longitudinal section of a costa, showing the base of two swimming plates. From an 



embryo in Stage III. 530/,. 



— 8. A colloblast. 53°/,. 



— 9. Young muscle cells from the mesodermal tissue (of a grown specimen). Cell-limits are 



somewhat distinctly indicated. (After an unstained preparation directly from a formaline- 

 specimen; the nuclei therefore appear as clear bodies within the granular mass of the cells). +'5/j. 



— 10— II. Vertical sections through the tentacle-rudiment of an embryo in the II. Stage. 10 is lateral, 



II median. Shows the beginning formation of the tentacle-sheath. The nuclei are in places 

 (fig. 10 in the lower part) serially arranged. 175/j. 



— 12—14. Three consecutive vertical sections, parallel to the transversal plane, through an embryo 



in the III. stage. Fig. 12 shows the opening of the right tentacle sheath, fig. 14 of the 

 left. Fig. 13. — comp. PI. VII. Fig. 3. For the rest the figures are easily understood from 

 the accompanying letters. 75/,. The limit between the large entodermal cells and the meso- 

 dermal tissue indistinct. 



