Plate I. 



Ki};. 1 :i. Two ooecia of Flustra papi/racea Ellis ami 

 Sol. The proximal ciul of the opercular 

 muscle of the (xicium is seen between the 

 zod'cial o])erculum and the otceium. X 23. 



— 2 a. A loiifiitiidinal section throiif(h an oieeium 



of /'/iis/ra nwrnhraitacco-truncald Smitt. A low 

 cry])t()cyst belt is seen between the o(ecium 

 and the coverin)^ membrane (the ectoo(icium). 

 The membranous wall separating the ziKccium 

 from the ixvcium is incorrectly indicated as 

 the muscle of the oa-cial operculum. I'his 

 muscle is not seen in the figure. X 40. 



— 2 b. An ocecium of the same species fmm the 



frontal aspect. The pro.ximal part of the 

 od'cium is covered with a cryptocyst belt, 

 and the pro.ximal ends of the muscles of 

 the ooecial operculum are .seen between this 

 belt and the zooecial operculum. X 40. 



— 3 a. An oiucium of Flustra Barlcei Busk. The 



same parts as in I-"ig. 2 b arc seen here. X 40. 



— 4 a. Flustra (Spirataria flnslroides vHincks , with 



od'cia. The two pro.ximal oacia arc com- 

 pletely covered by the cryptocyst belt, whilst 

 the four distal show the latter in difl'erent 

 degrees of development. X 40. 



— 4 b. An ocecium of tlie same species, enclosed in 



an avicularium. X 40. 



— 4 c. Two od'cia of the same species; lateral view. 



X 40. 



— 5 a. Longitudinal section through two oa'cia of 



Flustra securifrnns (Pallas\ X 40. The 

 muscle of the 0(ccial operculum (m. ov.) is 

 seen in the angle between the oa'cial oper- 

 culum and its inner membranous continua- 

 tion, d. w. cryptocyst process. 



— a b. An od'cium of the same species from the 



frontal surface. The ocecial operculum, the 

 pro.ximal end of its muscle and the two 

 cryptocyst processes id. w.) are seen between 

 the oa'cium and the zooecial operculum. X 40. 



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



a zod'cium with oa'cium. The oiecial muscle 

 and the two crvptocvst processes are seen. 

 X 40. 



— () a. A zooecium with (xecium of Flustra {Kcli- 



Pustra) cribrifonnis i Husk . X 40. 



— () b. The same species, from the basal surface. 



The uncalcified longitudinal belt is more 

 dilated at the distal end of the three zooc- 

 cia with oreeia. X 23. 



— 7 a. Flustra Retiflustra; Schonaui n sj).. with 



a pear-shaped avicularium. The cryptocyst 

 of the zoa'cia shows lines of growth. X 40. 



— 7 b. A young zooecium with ouccium. of the same 



species. X 40. 



— 7 c. An older zotrcium with oncium, of the same 



species. The proximal part of the ofccium 

 is covered by a cryptocyst belt. X 40. 



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



X 23. 



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



foliacea L. X 40. 



— 8 b. Two oiL-cia of the same species, lateral view, 



d. w. the distal wall. X 40. 



I'ig. a \ zoirciuni with orecium of Flustra (Spiral- 

 <iri(i denliculatii Busk. The oiecium is en- 

 closed in an avicularium. X 40. 



— 10 a. F'arciniinaria uncinata Hincks, wirli od'- 



cium. X 23. 



— 10b. The .same species. The ooeciuni and the 



surrounding kenozonccium. lateial \ iew 

 X 23. 



— 10 c. The same species. The 0(eciuni partly from 



the basal surface. X 23. 



— 10 d. The same species. A longitudinal section 



through the gouozoiecium, the ocrcium and 

 the surrounding keuozoa?cium. The distal 

 wall d. w.) between the gonozooccium and 

 the kenozotecium is seen. m. ov. the meiu- 

 branous wall separating the zo(ecium from 

 the oiecium. X 23. 



— 10 e. A longitudinal section through the same 



parts but parallel to the frontal wall of 

 the gonozocecium. The angular distal wall 

 between the gouozoa-cium and the keno- 

 zocecium is seen. X 40. 



— 11a. Nellia ajipcndiculata (Hincks!. The two 



proximal zoa'cia with ocecia. X 40. 



— lib. The same .species. A longitudinal section 



through two zocccia with ocecia; only the 

 endi)o(xcium is seen whilst the likewi.se 

 calcilied ectooiecium has been overlooked, 

 m. ov. the membranous wall between the 

 zo<ecium and the oiecium. X 40. 



— 12 a. Two zo(ccia with oiecia of Columnaria 



borealis n. sp. On each side of the ooccium 

 In its distal half is seen a cryptocyst olate. 

 X 17. 



— 121). The same species. The membranous ecto- 



oa'cium and the triangular cryptocyst plate 

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



— 12 c. Some zotveia 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- 

 tocvst plate of the ooecium (ekto) are seen. 

 X '23. 



— 12 d. A longitudinal section through a zo(ecium 



with (xecium. The membranous ectoocecium, 

 the cryptocyst plate eklo' of the od'cium 

 and the membranous wall between the 

 zoa'cium and the oiecium (m. ov.) are seen. 

 X 23. 



— 13 a. Xellia tenella (Lam.). All the zocccia with 



o(ecia. X 100. 



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



eia to the left without ofccia. An avicul- 

 arium chambci' is seen through one of the 

 lateral walls of the middlemost zocccium. 

 X 40. 



— 13 c. A zoci'cium with occcium. The ectoocecium 



shows an uncalcified transverse belt. X 75. 



— 13d. A longitudinal section through an ocecium 



of the same species. The membranous parts 

 are not seen and the calcified ectooiecium 

 is by a mistake not separated from the 

 endocxrcium. X 40. 



— 13 e. An avicularium of the same species with 



pit for the insertion of the radical fibre. 

 X 200. 



