17 
rior part of the zooecium, whose orifice opens into the bottom of 
the ocecium. The two valves composing the latter can perhaps be 
regarded as corresponding with the two little spines present in the 
other zoo0ecia. 
8) The acanthostegal ocecia, which are only found in two spe- 
cies of the genus Electra (E. zostericola and E. amplectens) are 
cavities internally limited by the covering membrane of the zooecium 
and externally by a cover made up of two rows of hollow spines. 
Ås to the way in which the eggs get into the ocecium, in 
respect "to the epistomial, the peristomial and the valvular 00ecia, 
there can be no doubt that the migration must take place through 
the orifice of the zooecium, which opens directly into the ocecium. 
As the hyperstomial ooecia have their place quite outside the zooe- 
cial wall in which there is no perforation, here neither can we have 
any doubt that the eggs do pass into the oocecium by this way and 
the same must be the case in Frustridae and Farciminariidae, in 
which the o0ecial, and the zooecial cavities are separated by the 
lower membranous half of the ocecium. According to Calvet!), in Ce/- 
laria there exists an opening in the calcareous wall between the z00e- 
cium and the ooecium. I must however deny the existence of such 
an opening which I have not been able to find even- by grinding 
the colonies in several directions. Though we at present only 
know the calcareous parts of those o0ecia, previously referred to the 
endozooecial 00ecia, it is not probable that there should here exist 
an internal connection between the zooecium and the ooecium, there- 
fore I must suppose that in all Cåeilostomata the migration of the 
egg from the zooecium into the ocecium, must take place through 
the" orifice. At first glance the supposition may perhaps appear 
strange that the egg should first pass out through the orifice of 
the zooecium and afterwards enter the oocecium through its outer 
Opening, but firstly there is no other way left, and secondly I do not 
think that this passage will be much more difficult than that which 
1) Ops ett. pag. 265) Pl VD KØ 11 
Vidensk. Medd. fra den naturh. Foren. 1902. 2 
