Plate I. 



Fig. 1 a. Two ocecia of Flustra papyracea Ellis and 

 Sol. The proximal end of the opercular 

 muscle of the ooecium is seen between the 

 zooecial operculum and the ooecium. X 23. 



— 2 a. A longitudinal section through an ooecium 



of Flustra membranaceo-truncaia Smitt. A low 

 cryptocyst belt is seen between the ooecium 

 and the covering membrane (the ectoooecium). 

 The membranous wall separating the zooecium 

 from the ooecium is incorrectly indicated as 

 the muscle of the ooecial operculum. This 

 muscle is not seen in the figure. X 40. 



— 2 b. An ooecium of the same species from the 



frontal aspect. The proximal part of the 

 ooecium is covered with a cryptocyst belt, 

 and the proximal ends of the muscles of 

 the ooecial operculum are seen between this 

 belt and the zooecial operculum. X 40. 



— 3 a. An ooecium of Flustra Barleei Busk. The 



same parts as in Fig. 2 b are seen here. X 40. 



— 4 a. Flustra (Spiralaria) flustroides (Hincks), with 



ooecia. The two proximal ocecia are com- 

 pletely covered by the cryptocyst belt, whilst 

 the four distal show the latter in different 

 degrees of development. X 40. 



— 4 b. An ooecium of the same species, enclosed in 



an avicularium. X 40. 



— 4 c. Two ooecia of the same species; lateral view. 



X 40. 



— 5 a. Longitudinal section through two ooecia of 



Flustra securifrons (Pallas). X 40. The 

 muscle of the ooecial operculum (m. ov.) is 

 seen in the angle between the ocecial oper- 

 culum and its inner membranous continua- 

 tion, d. w. cryptocyst process. 



— 5 b. An ooecium of the same species from the 



frontal surface. The ooecial operculum, the 

 proximal end of its muscle and the two 

 crj'ptocyst processes (d. w.) are seen between 

 the ooecium and the zooecial operculum. X 40. 



— 5 c. The distal wall — from the distal end — of 



a zooecium with ooecium. The ooecial muscle 

 and the two cryptocvst processes are seen. 

 X 40. 



— 6 a, A zooecium with ooecium of Flustra {Reti- 



flustra) cribriformis (Busk). X 40. 



— 6 b. The same species, from the basal surface. 



The uncalcified longitudinal belt is more 

 dilated at the distal end of the three zooe- 

 cia with ooecia. X 23. 



— 7 a. Flustra (Retiflustra) Schonaui a. sp.. with 



a pear-shaped avicularium. The cryptocyst 

 of the zooecia shows lines of growth. X 40. 



— 7 b. A young zooecium with ooecium, of the same 



species. X 40. 



— 7 c. An older zooecium with ooecium, of the same 



species. The proximal part of the ooecium 

 is covered by a cryptocyst belt. X 40. 



— 7 d. The same species from the basal surface. 



X 23. 



— 8 a. Two egg-shaped ooecia of Flustra {Flustra) 



foliacea L. X 40. 



— 8 b. Two ooecia of the same species, lateral view, 



d. w. the distal wall. X 40. 



Fig. 9 a. 



10 a. 



10 b. 



10 c. 



— 10 d. 



10 e. 



11a. 



lib. 



— 12 a. 



A zooecium with ooecium of Flustra (Spiral- 

 aria) denticulata Busk. The ooecium is en- 

 closed in an avicularium. X 40. 

 Farciminaria uncinata Hincks, vArh ooe- 

 cium. X 23. 



The same species. The ooecium and the 

 surrounding kenozooecium. lateral view. 

 X 23. 



The same species. The ooecium partly from 

 the basal surface. X 23. 

 The same species. A longitudinal section 

 through the gonozooecium, the ooecium and 

 the surrounding kenozooecium. The distal 

 wall (d. w.) between the gonozooecium and 

 the kenozooecium is seen. m. ov. the mem- 

 branous wall separating the zooecium from 

 the ooecium. X 23. 



A longitudinal section through the same 

 parts but parallel to the frontal wall of 

 the gonozooecium. The angular distal wall 

 between the gonozooecium and the keno- 

 zooecium is seen. X 40. 

 Nellia appendiculata (Hincks). The two 

 proximal zooecia with ooecia. X 40. 

 The same species. A longitudinal section 

 through two zooecia with ooecia; only the 

 endoooecium is seen whilst the likewise 

 calcified ectoooecium has been overlooked, 

 m. ov. the membranous wall between the 

 zooecium and the ooecium. X 40. 

 Two zooecia with ooecia of Columnaria 

 borealis n. sp. On each side of the ooecium 

 in its distal half is seen a cryptocyst plate. 

 X 17. 

 12 b. The same species. The membranous ecto- 

 ooecium and the triangular cr3'ptocyst plate 

 (ekto) of the ooecium are seen. X 17. 

 Some zooecia of the same species, the mem- 

 branous parts of which have been removed. 

 The lateral walls and the distal wall (d. w.) 

 with rosette-plates in addition to the cryp- 

 tocyst plate of the ooecium (ekto) are seen. 

 • X 23. 



— 12 d. A longitudinal section through a zooecium 



with ooecium. The membranous ectoooecium, 

 the cryptocyst plate (ekto) of the ooecium 

 and the membranous wall between the 

 zooecium and the ooecium (m. ov.) are seen. 

 X 23. 



— 13 a. Nellia tenella (Lam.). All the zooecia with 



ooecia. X 100. 



— 13 b. The same species. The two proximal zooe- 



cia to the left without ooecia. An avicul- 

 arium chamber is seen through one of the 

 lateral walls of the middlemost zooecium. 

 X 40. 



A zooecium with ooecium. The ectoooecium 

 shows an uncalcified transverse belt. X 75. 

 A longitudinal section through an ooecium 

 of the same species. The membranous parts 

 are not seen and the calcified ectoooecium 

 is bj' a mistake not separated from the 

 endoooecium. X 40. 



An avicularium of the same species with 

 pit for the insertion of the radical fibre. 

 X 200. 



— 12 c. 



13 c. 



— 13d. 



13 e. 



