586 E. A. MINCHIN. 



Figs, 33 — 37. — From sections of adult Clathrina reticulum. 



rig. 33. — A young quadriradiate spicule with formative cells; the basal 



rays, two of which appear in the section, have each two formative 



cells. The gastral ray is completely enveloped in its actinoblast. 

 Kg. 34. — A slightly older gastral ray with its actinoblast. 

 Fig. 35. — Gastral ray apparently fully formed, the actinoblast with its 



single nucleus having retreated to the extremity of the ray. 

 Fig. 36, — Gastral ray with actinoblast in which the nucleus has only 



recently divided, at a late stage in the growth of the spicule. 

 Fig. 37. — Yery long and slender gastral ray, with two nuclei in the 



actinoblast, 



PLATE 41. 

 All the figures refer to Clathrina contorta. 



Fig. 38. — Surface view of the oscular rim in the region just above the 

 limit of the collar-cells. Gastral aspect. The preparation contains eight 

 porocytes, one with two nuclei; a quadriradiate spicule, each basal ray 

 bearing the usual two formative cells, and the gastral ray enveloped in an 

 actinoblast with two nuclei ; and seven collar-cells, more or less completely 

 shown. To show the identity of porocytes and gastral actinoblasts. 



Fig. 39. — View of the gastral surface of the body-wall in a spot slightly 

 below that figured in the last figure, showing collar-cells and four poro- 

 cytes, three of them opened and functioning as pores. The collars of the 

 collar-cells are seen in optical section at higher focus as irregular circles, in 

 the centre of each of which the flagellum appears as a dot. 



Fig. 40, — Surface view of dermal epithelium of oscular rim on the outer 

 side. 



Fig. 41. — Section of oscular rim, showing epithelium as in Fig, 40 on the 

 lower side, and granular porocytic epithelium, as in Fig, 38, on the upper 

 side. The section being fairly thick, and being decalcified, shows the ground 

 substance full of spaces formerly occupied by spicule rays, to two of which 

 formative cells are adhering, and a gastral ray projects on the upper side 

 bearing an actinoblast with two nuclei. Note also four minute wandering 

 cells. 



Fig, 42. — An epithelial cell from the inside of the oscular rim, near the 

 margin of the osculum, intermediate in its characters between the ordinary 

 dermal epithelial cells and the porocytes. 



Fig. 43. — A granular wandering cell. 



Fig. 44, — A granular wandering cell near two sexual cells (spermatogonia?). 



Fig. 45. — Two sexual cells similar to those in the last figure. 



Fig. 46. — A finely granular wandering cell (the fine granules only drawn in 

 part). 



