paid to their distribution within the host’s corallum.

Abstract: Organisms of unknown biological affinities, assigned to the genus Chaetosalpinx, are known to infest Palaeozoic tabulate corals and stromatoporoids. Analysis of distribution of these parasites, performed on Emsian–Eifelian material of Favosites goldfussi (Anthozoa, Tabulata) from the Northern Region of the Holy Cross Mountains (Poland), shows that parasites were absent in the early astogenetical stages, and that during astogeny both the absolute number of para-sites per colony and the number of parasites per polyp were increasing. The latter can reach 2.7 parasites per polyp. Preferred settling places are in corallite corners (junction of three individuals), but dense infestation also produced settlement in the corallite walls (between two individuals). Probable causes of the increase are insufficient protection by host’s cnidae, insufficient immune system response, and parasite ability to adapt to the host’s defences. Endobionts belonging to the genus Chaetosalpinx (and other closely related genera such as Helicosal-pinx) inhabited coralla of various tabulate corals (Tapanila 2005). They were originally considered as their commensals (e.g. Oekentorp 1969), but Stel (1976) suggested that they may be parasites. A recent analysis (Zapalski 2004, 2007) has shown that the relation between them and their hosts was parasitic rather than commensal. Howell (1962) pro-posed placing them among serpulids, but the biologi-cal affinity of these endobionts remains unknown. Although these organisms were often described and illustrated (e.g. Oekentorp 1969; Plusquellec 1968a, b; Tapanila 2002), very little attention wa