MATERIALS FOR A MONOGRAPH OF THE ASCONS. 587 



Fig. 47. — A finely granular wandering cell. 



Tig. 48. — A minute triradiate system in its sextet of formative cells. 



PLATE 42. 



All the figures refer to Clathrina contorta. 



Fig. 49. — View of the gastral surface of the body-wall, showing, amongst 

 the collar-cells, a porocyte in continuity with a gastral actinoblast, which is 

 overlying a young triradiate system. The gastral ray has not made its appear- 

 ance. Only the gastral aperture of the pore has been figured, and the forma- 

 tive cells of the triradiate system have also been omitted. 



Fig. 50. — A similar view of a slightly more advanced stage. The porocyte 

 has the dermal aperture closed ; the minute gastral ray has now appeared. 



Fig. 51. — A similar view of still older stage. The gastral actinoblast has 

 completely separated from the porocyte, and the nucleus of the former has 

 divided into two. 



Fig. 52. — Slightly older but rather anomalous stage. The gastral actino- 

 blast has its nucleus divided into two, but is still in continuity with the poro- 

 cyte. Collar-cells not figured. 



Fig. 53. — Young quadriradiate showing the gastral ray a little from the 

 side, enveloped in an actinoblast with two nuclei. 



Fig. 54. — More advanced stage. The actinoblast now has four nuclei. 



Fig. 55. — Fully formed gastral ray, from a section. The large actino- 

 blast is spread over the gastral ray like a plasmodium, and contains four 

 nuclei. 



