4 
frame we find in a smaller number of species (for instance in Fl. 
carhasea, Fl. denticulata, Fl. hiseriata etc.) a little under the mem- 
brane a narrow, calcified band in connection witb tlie side walls and 
with the proximal wall. InWaters’ paper on Flustridae'^) we see 
this band, which the author signifies as „chitino-calcareous band“, 
in a cross-section of Fl. hiseriata. This calcified band in the 
named .FZws^ra-species is the first faint beginning of the calcified 
front wall, and in Membrani'poridae we find it developed in very 
different degrees. While in a number of species it is either absent 
or only developed in the same degree as in the above named Flu- 
sir«-species, in others it extends over most part of the front sur- 
face. While in some cases as for instance in Chaperia annulus^) 
it is concave in its whole extension, in other species it is convex 
in most part of its surface and only concave within the margin of 
the membranens area^). That the membrane covering this calcified 
layer is really the original membranous surface of the zooecium is 
evident from the faet that it is continuous with the opercular mem¬ 
brane. Also in Coilostega and Camarostega the calcified front wall 
takes its origin under the original membranous covering of the 
zooecium and in connection with the calcified frame which can be 
easily seen in the growing edge of the colonies. Like H a r m e r 
I have seen in several forms that the compensation-sac takes its 
rise beneath the proximal edge of the operculum, and although I 
have not yet examined its development by means of longitudinal 
sections I cannot doubt that it is formed by an invagination of 
the covering membrane. The view here proposed of the morphology 
of the front wall perfeetly agrees with the researches of L. C al ve t^), 
this author having found that the calcified front wall both in Coi- 
Journ. E. Mie. Soc. 1896, PI. VIII, fig. 6—8cb. 
Waters, On Membraniporidae, Journ. Linnæan Soc. Zool. Vol. XXVI, 
PI. 47, fig. 5. 
0 loco. cit, PI. 47, fig. 19. 
*) Contributions å l’histoire naturelle des Bryzoaires éctoproctes marins. 
Montpellier et Paris, 1900. 
