Plate XIX. 



I"if(. \ .\ rniiKislaja ivniislit iNi)iman\ A zocvcium Fi^. >S li- 

 mikI two (Iwaif-zod'cia. X 75. 



— 1 li Till' samo species, from the basal siirl'ace. , 



Two oii-eia are seen siirniuntlcd l)y dwarf- — i) a. 

 zocrcia, which, Hke the ordinary zorecia, 

 are fnrnished willi pore-chambers. X 40. 

 1 c .\n opcrcnium of the same species. X 149. 



— 1 (I. .\m operculnm of a dwarf-zocccium. X 200. 



— 2 a. Disco/iora piironclla (Alder. . \ portion of 



tlie marf^in of a colony witli all the zooccia 

 undeveloped. On the oldest zodceia the dcvel- — i) b. 

 opmeiit of the a\ icnlaria lias just bcgnii, 

 lint the frontal surface of these is still a 

 cimtiiuious membrane, and on four zod'cia I ID a 



the frontal surface still consists of a row 

 of independent calcareous jilates separated 

 by sutures. Distally to these plates is seen -- 1(1 b. 

 a dark curved line, the j^rowiujj end of the 

 fold which encloses the cryptocyst, and the 

 internal layer of which becomes the exter- 

 nal wall of the compensation-sac. X 2,3. — 10c. 



— 2 b. .\ sagittal .section Ihrongli a zo(Cciuni of the 



same species to show the compcnsation-sae 

 (es\ The above-mentioned fold surrounds — 11a. 

 parts of the decalcilied. broken cryptocyst i — 12 a 

 (cr.). X 75. 



— li a. The zocteia of Smillina jiroiiiiiqiia (Smitt), I 



from the basal surface, which consists of a I — 13 a. 

 number of striated plates meeting in sutures. 

 X 4(1. 



— 4 a. Snullina Sinitli Kirchenp. A developing i — liib. 



o(ecium. The ectooiecium still consists of 



two separate halves. X 40. — 14 a. 



— 5 a Smillina palnxtla (Sars), var. A developing 



od'ciuni. X 40. 



— 5 b. The basal surface of a zocccium of the same — 15 a 



species. Plate-mosaic with centres of calci- 

 fication. A multiporous rosette-plate. X 40. — 15 1) 



— (i a. X zoiecium of Sniillinii Lanshoroi'i (.lolinst.) 



with oa-cium. An occcial cover is seen, which — 16 a 

 paitly appears in the margin of the zore- 

 ciiini partly forms two projections distally 

 to the aperture. X 40. 

 r> b .\n od'cium of the .same species, through — 17 a 

 the broken ectocicium of which the ciido- 

 ou'cinm is seen. X 100. 



7 a. Two (Hccia of Smittinn Irispinusa, var. nicul- 



Ictna n. with a hood-shaped oiecial cover. X 40 



8 a. Some zcxucia of I'liisira seciirij'rons (Pall.) 



after boiling in potash, to show the process 

 of calcitication of the basal wall I'see pages 

 4-5). X 33. 



«li— f. Sagittal sections through a series of devel- 

 oping oa-cia of the same species (see page 

 57). X 40. 



Kg. A very early rudiment of an otecinm of the 

 •same species seen partly from the proxi- 

 mal end. The distal curved line is the line 

 in which the distal wall joins the frontal 

 membrane (fig. 8 b\ and the bilobatc part 

 .seen within the operculum belongs to the 

 horizontal part of the distal wall. The 

 rounded sinus is the beginning of the ro- 

 sette-plate. X 40. 



— 18 a. 



— 18 b 



— 18 e. 



— 19 a 



-II. .\ series of (kvclopmcnlal stages of the 

 endoocrcium of the same species, seen from 

 the surface. X 40. 



Some zocecia of h'liislrii (Flustra fnliiiceti L., 

 from the basal surface, after boiling in po- 

 tash. The distal wall with its rosette-plates 

 is seen and the composition of the basal 

 wall in small plates see page (i). .A very 

 tine striation parallel to the distal lines 

 cannot be seen in this figure. X 40. 

 Two zotrcia of the same species after boil- 

 ing in potash. The lateral wall's composi- 

 tion of small plates is seen. X 40. 

 .\ transverse section through a branch of 

 Flustra (Spiralis) ilvnticnUdu Husk, cr. : 

 cryptocyst. X 55. 



.\ sagittal section tlirongli an avicularian 

 mandible of the same species, to show the 

 internal cavity which corresponds with the 

 vestibular cavity in the o])ei'ciilum. 

 A portion of the basal surface of the same 

 s|)eeies, to show its composition of cell-like 

 small plates icell-mosaic \ Inimers. 

 Operculum of l-'liistra pisciforniis. X 23. 

 .\ transverse section through a branch of 

 I'liistra Flustra) carhacea Sol. cr. : crypto- 

 cyst. X 40. 



An avicularian mandible of Sarsipaslra 

 ahyssicola (Sars. , to sliow Ihc internal 

 cavity. X 23. 



A transver.se seeliiin through the same 

 mandible in its middle part. X 23. 

 .\ trans\er.se section through an avicularian 

 mandible of an Onijchocella species, to show 

 the mandibular cavity. X 40. 

 The avicularian mandible of Snilin'lla 

 plaijiostoma lUisk. X 75. 

 .\ transverse section through the end of 

 the same mandible. X 75. 

 Pore-canals of .1/yr/oroiim suhnracile d'Orb. 

 Kacli of them contains an eiidosarcal cord 

 and is, at its |)roxinial part, furuished 

 with a unii)orous ro.sette-plate. Immers. 

 llasau'llia aiiriciilala (Busk). Kach of the 

 two-layered stalked, developing otrcia is 

 placed in a hollow. X 40. 

 A sagittal section through .some o(eciiim- 

 bcaring zoacia of Sclerodomiis dcnliciilnlus 

 (Husk\ The avicularium is seen on the 

 internal surface of the peristome and the 

 plate originating from the distal wall. X 23. 

 .\ sagittal section through a zo(ecium with 

 od'cium, more highly magnilied X 4(1. 

 The same species. As a portion of the 

 frontal surface has been ground away, the 

 Hat proximal part of the (Kccial frontal 

 surface is seen and the broadened crenul- 

 ated margin of the plate originating from 

 the distal wall. X 40. 



Discopora plicaki (Smitt.). The distal of the 

 two angular lines is the growing cud of 

 the fold or outpushiug formed by the 

 frontal membrane and enclosing the cryp- 

 tocyst whose growing end forms anotlier 

 angular line. X 40, 



