11 
the pores is divided in a number of triangular areas by calcified 
rays. Finally it shall only be stated that the „pores“ of the ooe- 
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 ooecia, AVheu I here try to give a general view of the 
different types of ooecia and their distribution among the Bryozoa 
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 ooecia. 
1) The endozooecial ooecia. These ooecia which are seated in- 
ternally between two contiguous zooecia in the same longitudinal 
row but as a rule chiefiy project into the bottom of the higher one, 
are best known in the idLmWj Flustridae. As shown byVigelius^) 
such an ooecium 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 sér- 
ving to open the ooecium. Vigelius is not right in his suppo¬ 
sition that the lower membranous half of the ooecium later disap- 
pears, and 1 have found it still existent in ooecia containing eggs. 
Hence follows that the cavity of the ooecium is always perfectly se¬ 
parated from the zooecial cavity. In Flustra foliacea also the lower 
half of the ooecium is calcified. In a number of species (f. i Fl. 
memhranaceo-truncata, Fl. Barleei, Fl. Jlustroides etc.) a calcified 
band is formed between the lower margin of the calcified part of 
M Bijdragen tot de Dierkimde, 11. Aflevering, 2 Ged. 1884, p. 47, 
Tab. 3—4. 
