14 



calcareous band in Fl hiseriatu. begins a little l)el()\v tbe up])er edge ni" llie ver- 

 tical wall of the zotrcia. This Cryptocysl reaches a somewhat greater develop- 

 ment in Fl. cribriformis and /•"/. Schaiund (PI. 1, fig. 7 a, 7 c), in which it shows 

 a varying number of lines of growth, according lo the age of tlu' zoo-ciuin. W'e 

 may mention finally, that while the zotrcia in the free pari of Fl. [oliacea have 

 no Cryptocyst, such is rather highly developed in the incrusling part of the coi- 

 lony and al.so, that it is well-develoi)ed in the avicularia of this s])ecits. 



Of the forms which we have here classed to the i'ainily l-'nrciiiiiiKiriidnc, the fiontal 

 wall of most of them has neither a Gymnocyst nor a Cryptocyst, or there is only 

 a faint trace of the last. On the other hand both of them appear rathei' well-developed 

 in Fdrciininaria appendicnlala (PI. 1, fig. 11) and in Xcllid Icnella (Pi. 1, fig. 1^). 

 Within tlie family Bicellariidae we find a completely membranous frontal wall in 

 most of the species referred to the genera Ihiskia, lieaniu and Diachoris. The 

 Gymnocyst reaches its greatest development in Dintclopia and Hicellarui, because 

 it may here attain more than half the length of the zoct'cium (PI. IV, fig. 5 and 8), 

 while it only has a small extension in most of the Bugiilu species. With excep- 

 tion of Bicellaria grandis (PI. IV, fig. 5 a), in which species we find a large distally 

 freely projecting Cryptocyst lamina, I have not been able to find any trace of a 

 Cryptocy.st in any other Bicellaria; still it seems as if a slightly developed Cryp- 

 tocyst can be found in almost all other members of the family, at least in the 

 older zott'cia, in which it often seems to be represented by the proximal part, 

 which shows distinct lines of growth. The whole of the Cryptocyst shows distinct 

 lines of growth in the figure of the zoa'cium of Maplcsloiiia simiilc.v shown in 

 PI. IV, fig. 9 a, but the proximal part is only slightly developed. With exception 

 of the Flustra-Vike Hoplilella armata (PI. II, fig. 10 a), in which the whole of the 

 frontal wall is membranous, a larger or smaller part of this wall is calcified in the 

 rest of the members of the family Scnipocellariidcc, and they have as rule a Gymnocyst 

 as well as a rugged or grained Cryptocyst, which in Cellularia ornala even seems 

 to form the whole of the calcified i)arl of the frontal wall. The Gymnocyst 

 however forms most fre(|uently the major part of this wall, and its proximal part 

 in Menipea acideala and Men. clau.sa attains nearly the two-thirds of the length of the 

 zoa-cium. The Cryptocyst seems to he strongly developed in most of the Caberea 

 species. While the whole calcified part of the zoa>ciimi in the Aeteidac is formed by 

 a Gymnocj'st, the conditions are very variable within the large family Mi'inbrani- 

 poridae. While the whole frontal wall is formed by membrane in Meinbranipora 

 nieinbranaceu and related species, a larger or smaller part of it is calcified in 

 most of the remaining forms, and this calcification is sometimes represented 

 only by a Gymnocyst, sometimes only by a Oyptocyst and sometimes by both. 



