13 



concludes rightly therefore in saying that the calcification, which ajjpears within 

 the marginal spines in the primary zoircinm of Schizoporella uuUjarh, is a Cryp- 

 tocyst, and such is found at the same place in many malacostegous Cheilostomala. 

 A Cryi)locyst of this sort is not only very plainly hollow or depressed, which is 

 in contrast to the arched Gymnocyst, hut also varies as a rule from the latter by 

 having a more or less grained or rugged surface. 



We can find all sorts of transitions hetween a completely membranous and 

 completely calcified frontal wall among the forms without a compensation sac, 

 and for which we have suggested the name: Auasca. The whole calcified part 

 is sometimes a Gymnocyst, sometimes a Cryptocyst and sometimes, both kinds 

 of calcification may appear at the same time, the Cryptocyst s])ringing from the 

 Gj'ninocyst where the latter passes over into the membranous area. We can dis- 

 tinguish between a distal part, a [)roximal part and two lateral [)arts for the 

 Gymnocyst as well as for the Cryptocyst. The distal ])art is in most cases the 

 least developed because of the position of the aperture in the distal part of the 

 zoo'cium, and may in the Cryptocyst not seldom be (juite missing, while the 

 proximal part as a rule has the largest extension. A peculiar excejjtion is found 

 in the form which Busk describes as Diaclioris magellanicd, i>. (Iistans\ but which 

 must undoubtedl}' be regarded as an independent species. The proximal part is 

 here very feebly develoi)ed, whilst the two lateral regions are verj' broad and 

 only separated by a split in the middle line of the zoo'cium. hi very few cases, as in 

 Membranipora delicatiila, the proximal part may grow out as a tree lamina which 

 is not connected with the lateral regions, and when such a lamina again meets 

 these (listally we have the peculiar condition known in Calesclutra denlknlala, in 

 which the frontal wall is furnished with two long and narrow fissures. The distal 

 part may in some avicularia, for instance in the lyre-shaped forms, exceed in 

 extent the proximal (PI. Via, fig. la, 2a, 3a). While a Gymnocyst in the Flus- 

 tridue is either (juitc lacking or only rej)resented by a faint marginal part, 

 there can in a number of species, as e. g. 7*7. denticulatci, Fl. ccirbacea, Fl. serrii- 

 lata, Fl. biseriula, Fl. cribriformis and Fl. Schenaiii, n. sp., appear a feeble, more 

 or less knotted Cryptocyst, the proximal |)art of which is most developed. While 

 the Cryptocyst appears very late in Fl. dei)liculata and therefore can only be 

 found in older ])arts of the colony, we find it very early developed in Fl. serru- 

 lala and Fl. carhasea, in which species it is only lacking in the very youngest 

 zooecia. Longitudinal and Iransverse sections through such a colony (PI. XXI, 

 fig. 10 a — 12 a) show that this Cryptocyst, which Waters'- calls the chitino- 



' 8. p. .'ji); ■■' 109, p. 28(1. 



