9 
sponding with as maiiy pore-chambers in the anterior half of a 
neighbouring zooecium. As can be seen in the growing edge of a 
colony, originally only the inner wall in which the rosette-plates are 
seated is present, and later the two other walls grow forth. Eo- 
sette-plates, or pore-chambers, are constantly present on all lateral 
and terminal walls but are also in a number of species to be found 
both in the dorsal and in the front wall. In the dorsal wall they 
are rarely to be found in one-layered colonies f. i. in Beania radi- 
cifera which is fixed to its substratum by a great number of con- 
necting tubes, each of which takes its rise from a rosette-plate 
with a single pore. One or more pore-chambers are present on the 
dorsal wall of each zooecium in Mucronella castanea and Leprcdia 
dorsiporosa and, in the later at least, connecting tubes take their rise 
from the smaller of these pore-chambers. Also in Euthyris obtecta 
the dorsal wall is under the covering membrane provided with a 
number of rosette-plates with a single pore. Eosette-plates I have 
further found on the dorsal wall of more or less zooecia in a num¬ 
ber of species growing in two-layered colonies, namely in Flustra 
hiseriata, Beania nohilis, Porella elegantula, P. compressa, Thalamo- 
porella Smitti, Steganoporella magnilabris, Microporella marginata 
and Mie. flahellaris. On the contrary I have in vain sought for 
such rosette-plates in the dorsal wall of Flustra foliacea, Fl. se- 
curifrons etc. On the front wall rosette-plates are present in all 
the members of the family Onchoporidae -to which family I refer 
Onchoporella homhycina, Onch. hicornis., Calwellia Sinclairi, Urce- 
olipora dentata, Ichthyaria oculata and 7. {Carhasea) Moseleyi. The 
rosette-plates which have a single pore are as a rule seated in 
the foremost part of the body and the same is the case in Cahjm- 
mophora lucida and Euthyris obtecta. The marginal pores which 
can be met with in many Camarostega (f. i. in Mucronella Pea- 
chii, Smittia reticulata, Umbonella verrueosa etc.) and which in elder 
zooecia as a rule are seated in more are less deep pits or areolæ 
are really rosette-plates with one or more (f. i. in Umbonella verru¬ 
eosa) pores. In the quite joung zooecia they have their place im- 
