15 
of the distal zooecium. A feeble beginiiing to such an ooecial 
cryptocyst are the two above mentioned small calcareous plates 
foimd in some species of Farchninaria, and the calcareous band 
fonnd in some species of Flustra, In a number of forms (Mucro- 
nella Peachii, Muc. coccinea, Schizoporella Cecilii etc.) the ooecium 
apparently possesses only a single calcareous layer, but I have no 
doubt that it is really formed by the fusion of two layers. If we 
isolate the outer calcareous layer in a species possessing distinctly 
two-layered, pore-bearing ooecia we will find that the pores as those 
in the front wall of a zooecium are closed by a membrane, which 
however will disappear after some times boiling in a solution of 
caustic potash. On the contrary, if we examine an apparently single- 
layered, pore-bearing ooecium (f. i. of Mucronella coccinea) having 
been boiled in a similar solution we will find that each pore is 
closed by a calcareous membrane which no doubt is the endoooecium 
here coalesced with the cryptocyst. While the ooecia of Memhrani- 
poridae and Crihrilinidae can be compared with those of Cellu- 
lariidae in that their back wall is only formed by the endoooecium, 
in other forms f. i. in Reteporidae and in Ramphostomella the ooecia 
are in their whole extent formed by two distinet calcified layers 
and are as the ooecia of Bicellariidae free and separable, at least 
in the quite young zooecia. In most Reteporidae they get later 
firmly connected with the front wall of the distal zooecium by means 
of covering layers of calcareous substance from the front wall of 
the zooecium growing out over the ooecium. 
3) The epistomial ooecia. These ooecia hitherto only found in 
Thalamoporella are external, large, kidney-formed, two-layered 
structures whose inner layer takes its rise from the margin of the 
orifice while the outer layer is a continuation of the distal wall. 
I have not been able to find any covering membrane. The outer 
aperture of the ooecium is closed by a cup-shaped strongly chiti- 
nized operculum, at its base connected with the membranous oper- 
culum of the zooecium. In contrast to the hyperstomial ooecia which 
are seated outside the lower part of the distal zooecium, these ooecia 
