ITS SPECIES AND OVICELLS. 133 



Fig. 14. Tvbucellaria fusiformis, d'Orb. Transverse section. X 25. 



15. Tubucellaria ce7-eoides (Y[\. Sc^o\.). From Naples. Section showing the diaphragm 



(d) retracted ; op, operculum ; ts, tentacular sheath ; rs, position of the rosette- 

 plate ; p, polypide folded in the zooecium. x 85. 



16. Do. Section showing the diaphragm attached at one side to the operculum and at 



the other to the wall of the peristome, x 150. 



17. Myriozoum subgracile, d'Orb. Section showing the diaphragm {d) with the polypide 



withdrawn, x 85. 



18. Tubucellaria cereoides, var. chuakensis, var. nov. Section showing the peristomial 



ovicell containing a larva {I) ; also the diminutive polypide with the diaphragm 

 {d) and the plug {pi) closing the ovicell. X 25. 



19. Do. Section of the end of the diminutive polypide in the peristomial ovicell, 



showing the operculum {op) thrown back ; further on the diaphragm {d), beyond 

 which there is a growth, at the end of which the plug will ultimately be formed. 

 X 250. 



Plate 16. 



Fig. 20. Tubucellaria cereoides, var. chuakensis, var. nov. Section through two ordinary 

 polypides and two peristomial ovicells. This is an absolute copy of one section, 

 though in two or three cases where the operculum had not been well cut through 

 that detail had to be taken from the following section. In the peristomial ovicell 

 the plug is seen withdrawn from the opening, but this may only be the result of 

 decalcification and preparation, as changes are sure to take place when the 

 calcareous support is removed. The operculum (op) has opened the peristomial 

 ovicell for the passage of the diminutive polypide, and the position of the 

 tentacular sheath {ts) and diaphragm {d) can be followed. In this case there is 

 no larva in the ovicell, but apparently there has been one and the ovaria {ov) 

 would probably soon furnish others. The parenchym passing through the rosette- 

 plates is seen at rp. X 85. 



21. Do. Section of plug with diaphragm by the side. X 250. » 



22. Do. Section of larva. X 250. 



23. Do. Section of the polypide-wall just past the operculum. In the lower zocecia of 



fig. 20 these cogwheel cells are seen, x 25. 



24. Do. Section of ovarium in the neighbourhood of a rosette-plate showing the 



protoplasmic network attached to the ovarium. X 150. 



25. Do. Section of peristomial ovicell containing a larva. The diminutive polypide 



is shown and the plug {pi) to close the opening, also the remains of the rectum (r) 

 and the incysting portions of the digestive tube (dt) are cut through. The ovarium 

 {ov) is immediately below the diminutive polypide, and there are parenchym- 

 threads from it to one of the cysts. This apparently shows an earlier stage than 

 fig. 20, as we still have the indications of the complete polypide. X 85. 



LINN. JOURN. — ZOOLOGY, VOL. XXX, 11 



