Plate XIX. 



Rliahdocalyptufi victor Ij. P. 238. 



Fio'. 17. A jonng specimen (8. C. M. No. 227) attached to a HexactineUa 

 lorica. Nat. size. 



Fi<j;. l.S, Portion of the longitudinal section of a yoimg specimen. Above, 

 the oscular edge ; at the middle, the irrcgularl}' wavy chamber- 

 layer which loses itself close to the oscular edge. About .30 x . 



Fig. 19. Free edge of chamber- wall, gradually passing into trabeculfe. 

 440 X . This figure, as also all the following figures, was taken 

 from a young specimen of the size of a small apjile, hardened 

 in alcohol and stained with hfeniatoxylin. 



Fig. 20. Small portion of a section, drawn witli the microscope focussed at 

 apopyles of chambers. 300 x . c, old and empty tiiesocytes. 

 The darkly stained bodies are thesocyte spheres, e., free edge of 

 apopyle. /., film-like connecting membrane covering the gap 

 between four adjoining apopyles. g., freely communicating gap 

 (without a connecting membrane) between apopyles. 



Fig. 21. Portion of a paratangential section passing near the gastral surfiice. 

 About 40 x . ex., excurrent canals in cross- section, in., inter- 

 communicating lacnna?, the ultimate end of the incurrent canal 

 system. 



Fig. 22. Portion of a similar section, jiassing through the jieriphery of the 

 ehoanosome. A])out 40 x . Lettering as in above. Here the 

 ultimate l)ranches of excurrent canals are seen to form anastomos- 

 ing lacunas around the stem of incurrent canals. 



Fig. 23. Constructed figure to show in section the branching of canals and 

 the folding of the chamber-layer. Above, the dermal surface is 

 supposed to 1)0 seen in a slanting away position, ioi., ex., wall of 

 incurrent and excurrent canals seen en face. Below, the con- 

 tinuous crastral laver. 



