232 J. H. ASH WORTH, 



mesogloea, some of which send processes into the ectoderm. On the inner 

 side, the fibrils pass into small stellate nerve-cells situated just outside the 

 muscle processes of the endoclerm cells, x 300. 



Fig. 17. — Longitudinal section through the body wall of a polyp, to show 

 the general character of the ectoderm and endoderm cells, and also the 

 processes of ectoderm cells which penetrate the mesogloea and establish 

 connection with the endoderm. x 400. 



Fig. 18. — Longitudinal section of the ventro-lateral portion of the lower 

 third of the stomodseum. The chief feature shown is the large gland-cells, 

 some of which have discharged their contents and appear empty, while others 

 are in the act of discharging their secretion. x603. 



Fig. 19. — Transverse section on the end of a dorsal mesentery showing the 

 V-shaped mesenterial filament bearing cilia. x 600. 



Fig. 20. — Transverse section of the end of a ventro-la.teral mesentery to 

 show the general character of the endoderm cells, the giant flagelluin of one 

 of them, and the cells in the mesogloea. x 600. 



Fig. 21. — Transverse section of the end of the same mesentery taken 

 •25 mm. higher, showing three flagella occuring close together. x600.' 



Figs. 22, 23, 24. — Three flagella from sections of polyps to show their 

 various degrees of flexion. x 600. 



Fig. 25. — Two abnormal forms of flagella from sections. A from the 

 tentacle of a polyp, B from the portion of a ccelenteron in a stem. x 600. 



Fig. 26. — Endodermic myo-epithelial calls from teased preparations. In 

 connection with the one on the right there is a small stellate cell with three 

 long processes. This is probably one of the nerve -cells of the endodermic 

 portion of the nerve plexus, x 500. 



Fig. 27. — Isolated cells bearing flagella, from teased preparations. x 500. 



Plate XXII. 



Fig. 28. — Section of a stem at the edge of the umbellate summit, to show 

 the formation of a young polyp -43 mm. long (II. in table, p. 215). Note 

 that the endodern of the free portion of the polyp is thick, while that of the 

 inner part of the ccelenteron is thin. The neighbouring ccelentera are cut 

 very obliquely. x 50. 



Fjg. 29. — The superficial canal indicated by the asterisk in Fig. 9 enlarged. 

 The cells of the outer wall are longer and more columnar than those of the 

 inner wall. x 500. 



Fig. 30. — Thin transverse section (3 ^ thick) of the end of a ventro-lateral 

 mesentery, to which three very young sperm sacs are attached. In the one 

 to the right the primitive genital cell has divided into four, three only of 

 which are visible. x 500. 



