Plate V. 



Euplectella marshalli Ij. 



Figs. 29, 30. Early stages in the development of floriconie. The principals 

 inclosed in the scleroblast mass. Borax-carmine. 1000 x , 



Fig. 31. Portion of a mature floricome, still with the scleroblast-mass. Borax- 

 carmine. 1000 X . 



Figs. 32-34. Stages in the 'development of graphiocome. Borax-carmine. 

 1000 X . 



Fig. 35. Optical section through the terminal sheaf of a developing graphio- 

 come. Borax-carmine. 1000 x . 



Fig. 36. A small portion from the periphery in a section through the ledge, 

 showing the conuli supported by dermal hilt-rays, the cobweb of 

 trabecula3, &c. Borax-carmine. 300 x . — axL, archteocyte-congeries. 

 arch., archfeocytes. eh., fundus of flagellated chamber, s.c, subder- 

 mal cavity, th., thesocytes. 



Fig. 37. Chamber- wall (reticular membrane). Acid-fuchsin. 1,500 x. Above, 

 the membrane is shown as out of the focus; the flagella are here 

 visible either sidewise or in optical sections. The central dot in 

 the choanocyte nuclei represents the origin of a flagellum. Below, 

 at the right corner, four archreocytes (arch.) 



Fig. 38. Same with coarse refractive granules in the i)rotoplasm. Acid-1'uchsin. 

 1500 x . 



Fig. 39. Apopylar edge of the chamber-wall. Borax-carmine. 1500 x . — 

 ch.n., choanocytal nucleus, wi.m., marginal membrane, ir., trabecula. 

 tr. n., trabecular nucleus. 



Figs. 40, 41. Choanocytes in profile view. Acid-fuchsin. 1500 x. 



Fig. 42. Same in surface view, combined from views obtained at different 

 foci of the microscope. Acid-fuchsin. 1500 x. 



Fig. 43. Optical section showing incurrent lacunar s])ace between four 

 chambers. ]3orax-carmine. 1500 x . — i/i.r., membrana reticularis. 

 Other letterings as in fio-s. 3 G & 39. 

 Fig. 44. Groups of peculiar rod-like bodies (})robably nut belonging to tiie 



sponge). Borax-carmine. 1500 x . 

 Fig. 45. Trabecula from a certain specimen, with egg-like cells (.r) of various 

 sizes. Borax-carmine. 1000 x . — tr.n., trabecular nuclei. 



