Plate IV. 



Eupleclella marshalli Ij. 



Fig. 4. Gastral view of the wall. Sieve-plate at the upper end. Nat. size. 

 Fig. .5. yiiowing the bottom-plate. Photo, from a drawing. Nat. size. 

 Fig. 6. A young (22 mm. long), before the breaking through of parietal 



oscula. Nat. size. 

 Fig. 7. Skeleton of a young specimen (32 mm. long). Nat. .size. 

 Fig. 8. A young specimen, 42 mm. long. Nat. size. 

 Fig. [). A J'oung specimen, 63 mm. long. Nat ciz». 

 Fig. 10. Floricome. 440 x . 



Figs. 11-13. Three stages in fJiiricouK^ development. 440 x. 

 Fig. 14. Terminal of the immature floricome shown in fig. 13. With in- 



ceptional teeth. 1000 x . 

 Fig. 15. Sieve-plates of two young specimens (39 mm. & 48 mm. long) ; 



seen from above. 2 x . 

 Fig. 16. Dermalia of an average size. 300 x. 

 Fig. 17. Oxyhexaster. 400 x . 

 Fig. 18. Young oxyhexaster. 440 x . 

 Eig. 19. Portion of a graphiocome. 440 x . 



Fig. 20. Portion of a graphiocome after the loss of the terminals. 1000 x. 

 Fig. 21. Ldpliocome. 440 x. 

 Fig. 22. Space between the apopyles {ap.) looked at from the excurrent side. 



440 X . cm., connecting menibrane betvv. the apojiyles. iit.vi., 



marginal membrane of tlie cluimber-wall. /v., trabeculie. 

 Fig. 23. A portion of the dermal inembraue. A trabecula expanded intu 



a film-like band. 1000 x . Ir.n., trabecular nucleus, tli., an old 



tiiesocyte. 

 Fig. 24. Portion of a thesocytal mass, showing the development of thesocytes 



from archreocytes (seen on the left). From a section stained with 



borax-carmine. 440 x . 

 Fig. 2."). Four thesocytes from above. 1000 x . 

 Fig. 2(). Lower end of a basal anchoring spicule. 150 x. 

 Fig. 27. Oscularia in situ. Below, the oscular sdge. 50 x . 

 Fig. 28. Section through the wall. 25 x . — «.tY., archnsoeyte congerie.s. ch.L, 



chamber-layer, ex.tr., external traljecular layer. iii..tr., internal 



tral)ecular layer, on.'i/i., oscular membrane, osc, o.scularia. 



