JIATERIALS FOR A MONOGRAPH OF THE ASCONS. 585 



extremity, while another still bears both its formative cells; a very 

 young quadriradiatc, the basal rays enveloped in their sextet of 

 formative cells; the gastral ray contained inagastral actinoblast which 

 is still continuous with a pore-cell; and finally, a granular wandering 

 cell, partly covered by a spicule, and two minute wandering cells, 

 rig. 19a. — The porocyte and gastral actinoblast of the last figure drawn 

 separately. 



Fig. 20. — View of dermal layer, dermal aspect. The figure shows seven 

 cells of the flat epithelium, and a portion of another ; one pore-cell ; 

 portions of three triradiate systems, one bearing a spicule-cell at the 

 extremity of a ray, and the proximal extremity of a large monaxon 

 spicule, bearing two spicule-cells ; and finally a young quadriradiate 

 surrounded by the six formative cells of the basal system, and the 

 gastral actinoblast. 



Fig. 21. — A young quadriradiate surrounded by the six cells of the basal 

 system, and the gastral actinoblast. 



Figs. 22 — 36. — From embryos of Ascandra falcata. 



Fig. 22. — A sextet from an embryo of the third day of fixation. 

 Fig. 23. — A young triradiate system from an embryo of the same date. 

 Fig. 24. — An older triradiate system from an embryo of the sixth day. 

 Fig. 25. — A ray of a triradiate, with its two formative cells, from an 

 embryo of the same date. 



Fig. 26. — A fully formed ray, with its single cell, embryo of the same 

 date. 



Fig. 27. — "Young triradiate systems, with their formative cells, from 

 Clathrina cerebrum, embryo of third day of fixation. The overlying 

 nuclei of the flat epithelium are drawn in outline only. 



PLATE 40. 



Figs. 28 — 30. — From sections of Clathrina cerebrum, adult. 



Fig. 28. — Young quadriradiate with gastral ray enveloped by its actino- 

 blast. 



Fig. 29.— Fully formed spiny gastral ray with its actinoblast, con- 

 taining a nucleus and scattered granules of chromatin. 



Fig. 30.— Fully formed smooth gastral ray with its actinoblast, con- 

 taining a nucleus at the lower extremity, and an aggregation of 

 chromatin granules near the apex. 



Figs. 31 and 32. — From embryos of Clathrina reticulum. 



Fig. 31. — Young triradiate system surrounded by sextet of formative 

 cells ; the overlying nuclei of dermal epithelium drawn in outline only. 

 Fig. 32. — An older triradiate sjstem, with cells as iu last figure. 



