58 



a strong llexioii and alleralion in shape. Thus, wliili' Ihe angle between llie liori- 

 zontal and vertical portions of tlie distal wall in fig. 8 b is right, and in lig. 8 c 

 obtuse, it gradually becomes more and more acute on account oC the endooo'cium 

 bending backw^ards towards the basal wall of the zoa^cium, without doubt be- 

 cause of the counter pressure brought about by the growth-tension. While the 

 portion between the horizontal part ol' the dislal wall and the jjoinl of the 

 indentation has nearly the same length in the examined longitudinal sections, 

 the indentation on the contrary increases in length, and lastly the oa-cial fold 

 grows down over the oa-cial membrane, which not long before occupied most of 

 the frontal wall of the deveio|)ing oojcium. At the same time as the developing 

 orrcium is undergoing these ailerations in shape, the whole zoa'cium increases 

 considerably in size, and the horizontal part of the distal wall in length. 



As already mentioned in the above reference to Vi gel ins" investigations, he 

 believes that the ocrcial membrane dissolves later, so that the egg from Ihe zon^^ 

 cium can reach into the oo^cium, but this view clearly proves to be wrong from 

 the fact, that I have found eggs lying in the oa>cia in Fl. secnrilhuis and Fl. 

 memhranacco-tnincnla (PI. I, fig. 2 a), the floor of which is formed by such an 

 ooecial membrane on which the egg rests. The egg must therefore have come 

 into the ooecium from outside through the oax-iai ai)erture, and possibly Ihe 

 altered position of the ou'cial membrane is due to this transference. Fig.s. 8 g— 8 n 

 show a series of developmental stages of the oo'cium mentioned, seen from the 

 surface of the colony. In the earliest of these (8 g) the ascending part of the 

 distal wall has nol yet l)egun lo calcify, and the deej) sinus between the (wo 

 rounded projections comes from the not yet closed uniporous rosette-plate. The 

 other figures show the formation of the owcial bladder, its partial closure and 

 the formation of the two calcareous ribs. 



While the rest of the oa'cinm-bearing members of Ihe family have essenlially 

 the same structure of the ocrcia as Fl. securifrons, we find a rather difierent 

 structure in Fl. folincea (PI. I, figs. 8a, 8 b; PI. XXIV, fig. 8), as the oa-cia here 

 have an irregular egg-shape. Whilst, as already mentioned, a pair of cryptoeyst- 

 ribs occur in /•"/. securifrons proximally lo the operculum of the zocecium, in a 

 number of species, e. g. in Fl. ineinbranaceo-trimcata (Pi. I, figs. 2 a, 2 b, PI. XXIV, 

 fig. 6), 7-7. Barleei (PI. I. fig. ;5 a), /•'/. Schonatii (PI. I, fig. 7 c) etc., a more or 

 less developed cryptocyst-belt occurs just dislally to the free edge of the oa^cium, 

 between this and the covering membrane; the originally separated lateral halves 

 of this belt later fuse together. This belt reaches its highest development in /•'/. 

 fliislruides (PI. I, fig. 4a; PI. XXIV, Lig. 7) and it may in lime quite cover the 

 ooecia, which in this species exceptionally project distinctly on the surface 



