131 



wall has one multiporous plate. Besides dependent auiciiliirid, found in most 

 species, vibraciila may also occur on the hasal surface of the colonj% and these 

 are connected with the colony by an independent wall. The oa'cia are generally 

 hyperstomial with a wholly or partly calcified ectoooecium, more seldom endo- 

 zod'cial. In the latter case they are sometimes enclosed in kenozooecia. As a rule 

 radical fibres occur, sometimes springing from a rosette-plate (or a pore-chamber), 

 sometimes from a separate chamber connected with a vibraculum. The colonies 

 are always free, very branched, most frequently with uni- or few-seried zocecia, 

 generally consisting of a single layer and in most cases jointed by means of 

 chitinized transverse belts. 



While a smaller number of species (e. g. Hoplitella arniala, Menipea flabellum, 

 Men. spicata'^ and the Canda species), have a membranous frontal area, occupying the 

 whole or almost the whole of the frontal surface, a larger or smaller part of the 

 latter is in the other species occupied by an arched gymnocysl which in some 

 species (e. g. in Menipea aculeittd Busk and Men clausa Busk) may be up to two- 

 thirds of the length of the zooecium. While the cryptocyst in many species (e. g. 

 in the Scruiwcellaria species, in Caberea Ellisi, Menipea acnleata, M. cirrata, M. 

 palagonica) forms only a small depression in the margin of the aperture, it may 

 in other species fill a larger part of the aperture inside the membranous fronlal 

 area in the form of a somewhat depressed, generally finely granular lamina. This 

 cryptocyst attains its largest extent in Menipea spicata, Caberea Darwini and in 

 the Canda s|)ecies, but also in Men. flabellnm, Men. rohorata (figs. 7 b, 7 c), M. 

 crystallina, M. liuski and several other Menipea si)ecies it may attain a consider- 

 able development. We have already mentioned that a number of species possess 

 a wholly chitinized, simple o[)erculum. As in Dimorpbozoum nobile and Dendro- 

 beania Murraijana the distal wall consists of a basal, horizontal or slightly obli- 

 (pie and a frontal, strongly ascending i)art (PI. II, figs. 7 g, 7 h, 8 c), but while 

 in these two species the former portion is furnished with a single, large, multi- 

 porous rosette-plate, it has generally in this family a great number, of single- 

 [)ored plates which are variously grouped. On examining a zocrcium from the 

 frontal surface (PI. II, fig. 7 a), the horizontal pore-bearing i)art of the distal wall 

 is seen at a deep level at some distance proxinially to the distal end of the zool;- 

 cium, and this is seen most clearly after a previous boiling in caustic potash. 

 The avicularia always have their inner wall in common with Ihe zooecium on 

 which they are placed; but as I have succeeded in isolating Ihe vibracula in 

 some species {Caberea Ellisi, Canda arachnoidea, (kiberiella benemnnila, Scrupo- 



' 69, p 132. 



9* 



