ba i 
the pores is divided in a number of triangular areas by calcified 
rays. Finally it shall only be stated that the ,,pores'" of the 00e- 
cia are also closed by a membrane. 
While the authors who have hitherto examined the rosette-pla- 
tes have mainly used these structures in the description of the spe- 
cies, it is my conviction that they are to be regarded as some of 
the best and most constant systematical characters. 
The ocecia. When I here try to give a general view of the 
different types of ocecia and their distribution among the Bry0ozoa 
I must premise that I have not yet succeeded in getting fresh de- 
calcified material, and therefore my researches on the ooecia deal 
chiefly with the calcified parts of these structures, however, I hope 
later to be able to supply these researches. We can at present 
distinguish between 8 different types of 00ecia. 
1) The endozooecial ocecia. These ocecia which are seated in- 
ternally between two contiguous zooecia in the same longitudinal 
row but as a rule chiefly project into the bottom of the higher one, 
are best known in the family Fvustridae. As shown by Vigelius!) 
such an ocecium Commences as a vesicular invagination from the 
membranous front wall and later coalesces with the incompletely 
developed distal wall. As a rule only its upper half is calcified 
and in the angle between its lower membranous half and the mem- 
branous front wall of the zooecium is fixed a muscular string ser- 
ving to open the ocecium. Vigelius is not right in his suppo- 
sition that the lower membranous half of the doecium later disap- 
pears, and I have found it still existent in ocecia containing eggs. 
Hence follows that the cavity of the ocecium is always perfectly se- 
pårated from the zooecial cavity. In Flustra foliacea also the lower 
half of the ocecium is calcified. In a number of species (f.i Fi 
membranaceo-truncata, Fl. Barleei, Fl. flustroides etc.) a calcified 
band is formed between the lower margin of the calcified part of 
1) Bijdragen tot de Dierkunde, 11. Aflevering, 2 Ged. 1884, p. 47, 
ab. 3—4. 
