77 



for the relationship. On the other hand, the mode of calcification seems to have 

 only a slight systematic importance, because it often varies, not only within the 

 genus but also within the species (see pag. 5). 



The frontal wall. As we have already fully discussed the differences, wliich 

 occur in the structure of the frontal wall under the morphology of the zooecium, 

 we may content ourselves here with a brief reference to this question. While 

 Jullien and later Can u attach such a great systematic importance to the crypto- 

 cyst, that they on the basis of it divide the Cheilostomata into two main divi- 

 sions: Diplodermata and Monodermata, we can only from the investigations we 

 have made on its extension in the different families (see pag. 13 — 16) regard it 

 as an auxiliary character. It is for the present not easy to judge to what extent 

 it can be used as such, since in many cases it is difficult to decide, whether 

 dried or even spirit Bryozoa have a cryptocyst or not. We may for instance 

 mention, that out of the whole material, which the zoological Museum of Copen- 

 hagen possesses of Escharoides coccinea, only a very few colonies of the genus 

 show a distinct covering membrane. While the frontal wall in some forms, e. g. 

 in the species of the genus Electra, the members of the families Hippothoidae 

 and Catenariidae is only formed of a gymnocyst, and in others e. g. the Onycho- 

 cella species only of a cryptocyst, both modes of calcification are represented on 

 this wall in most of the Cheilostomata. The cryptocyst shows a very remarkable 

 condition in Steganoporella and Thalamoporella, as it descends more or less deeply 

 into the zooecium through two (more seldom one single) openings proximally to 

 the aperture and may even reach the opposite wall. Still more peculiar is the 

 condition it shows in the genera Cellularia and Membranicellaria, because the 

 surface of the colony is divided by a network of ridges into a number of areas, 

 which do not correspond at all with the real zocecia. We have also seen that 

 the calcification of the frontal wall may take place to a very varying extent, so 

 that we can find all possible transitions between a quite uncalcified and a quite 

 calcified frontal wall, and the characters derived from the different extension of 

 the calcification are therefore more or less relative. 



The pores. I have already called attention to the fact, that a number of the 

 so-called pores seem to have a similar structure to that of the rosette-plates; but 

 as time and material have not allowed me to carry through such an examina- 

 tion everywhere, I shall here under the name of pores include all pore-like 

 formations, which in contrast to the rosette-plates are situated on free surfaces. 

 The pores are certainly amongst the formations, which have the least systematic 

 importance, because in most families and genera where they appear, they are 



