Different food species cause modifications in the growth forms of bryozoan species. Under cultivation conditions a "stolonization of zooids" is possible in Bowerbankia spp. In some species, e.g. Conopeum seurati and Alcyonidium spp., the numbers of tentacles are influenced by external and physiological conditions. Observations on the brackish water Membraniporid Conopeum seurati are summarized, which revealed that maturity and growth of the erect form are effected by a complex of interdependent factors (colony size, food, temperature, salinity). It is stressed that greater attentions should br paid to the ecologial conditions by taxononoists and systernatists. Numerical inquiries and statistical comparisons which ignore the influences of external factors on the growht forms are questionable. Cultivated Bryozoa may develop forms which under natural conditions will not normally be realized, but which may be of systematic importance. A new cultivation apparatus for long term rearing of sessile plankton feeders has been developed. The experimental vessel of the apparatus has a U-bottom of perspex to sustain a vertical water rotation. The water movement is produced by water in a container vessel, raised above the level in the experimental vessel by an improved type of a bubble-pump. The experimental animals can be observed with a stereo-microscope or with a photo-apparatus without removal from the experimental vessel
