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nata and the incrusting Micr. ciliata as well as between a freely growing, richly 

 branched Japanese Microporella which is closely related to M. Malusi, and the 

 last-mentioned, as a rule incrusting species. Genera based on the presence of 

 radical fibres (e. g. Craspedozoum, Flustramorphd) will for these reasons be just 

 as artificial as genera based' on the form of the colony, but this does not ex- 

 clude that differences in the appearance of the radical fibres may sometimes be 

 of use as auxiliary characters, e. g. in some genera of the family Bicellariidae. 

 A much greater systematic importance must be given to the flat kenozooecia, 

 which in all freely growing Reteporidae not only form the incrusting part of the 

 colony but also a covering of its basal (as a rule the outer) surface. Although 

 on account of their position they can only occur in freely growing species, they 

 are namely characteristic for the family Reteporidae, and are found in all members 

 of this family, occurring as free colonies. A still greater systematic importance is 

 held by the lateral chambers, so characteristic of the family Catenariidae, which 

 may appear in each zocecium up to four in number on each side, and which 

 besides the importance they have for the distinction of the family also in many 

 cases offer good generic and specific characters. 



The Heterozooecia, as is known, may sometimes occur independent or vicarious, 

 taking the place of a zocecium in the colony, sometimes dependent and situated 

 on the zooecia, and in the last case they may in one waj^ be regarded as organs 

 belonging to these. The vibracles, which appear on the basal wall in Caberea and 

 other genera of the family Scrupocellariidae, occupy a peculiar intermediate posi- 

 tion between the independent and dependent heterozooecia; for while in other 

 cases the latter are always connected with the zooecia by a common wall, these 

 vibracles have an independent basal wall, and can therefore be separated from 

 the zooecia. The difference between independent and dependent heterozooecia is 

 of systematic interest, in that certain systematic divisions (families and genera) 

 only have independent heterozooecia, others only dependent, while again others 

 present both kinds, not seldom in such a way that they occur together. The 

 independent heterozooecia have their main extension in the division Anaska, 

 where they appear unmixed in the families: Flustridae, Celluladidae and Thalamo- 

 porellidae, besides in the genera Onychocella, Selenaria, Cupularia and Lunularia: 

 The majority of the Membraniporina and Cribrilina forms may have dependent 

 heterozooecia, though independent ones do appear in not a small number of 

 species, e. g. in Membraniporina crassimarginata, M. cornigera, M. pijrula, M. plana, 

 M. velata and in Figulina figularis. While all the other species of the genus 

 Callopora have dependent heterozooecia, we find at the same time independent in 

 C. craticula. Independent heterozooecia seem to occur in all members of the 



