I have written this book because there is, as in almost all supraspecific ciliate taxa, an ur- gent need for an up-to-date revision of the oxytrichids, which are common in terrestrial, limnetic, and marine biotopes. The last comprehensive, illustrated guides to this group of hypotrichs were provided by KAHL (1932) and SmLER (1974b); however, as regards syn- onymy and faunistics, these works are outdated and not as detailed as EHRENBERG'S out- standing book from 1838. In KAHL's revision, the oxytrichids sensu stricto are described on about 30 pages, whereas in the present book the systematic section comprises about 830 pages. This extraordinary increase in page number is mainly due to the following points: (i) Species number increased from about SO in KAHL to about 170 in the present book. (ii) KAHL usually provided only a single illustration of each species, whereas almost all published illustrations on oxytrichid ciliates are included in my book. (iii) Modern, phylogenetic systematics of oxytrichids without morphogenetic data is impossible; conse- quentlY,*almost all detailed descriptions, usually dealing with the type species, have been included. (iv) Synonymy is discussed, and not only mentioned, as is unfortunately usual.

The present monograph is the fourth of six volumes which review the Hypotricha, a major group of the spirotrichs. The book is about the Gonostomatidae, the Kahliellidae, and some taxa of unknown position in the hypotrichs. Gonostomum was previously misclassified in the Oxytrichidae because its type species Gonostomum affine has basically an 18-cirri pattern, which is dominant in the oxytrichids. A new hypothesis, considering also molecular data, postulates that this 18-cirri pattern evolved in the last common ancestor of the hypotrichs and therefore it appears throughout the Hypotricha tree. The simple dorsal kinety pattern, composed of only three bipolar dorsal kineties, and gene sequence analyses strongly suggest that Gonostomum branches off rather early in the phylogenetic tree. Thus, the Gonostomatidae, previously synonymised with the oxytrichids, are reactivated to include the name-bearing type genus and other genera (e.g., Paragonostomum, Wallackia, Cladotricha) which have the characteristic gonostomatid oral apparatus. The Kahliellidae are a rather vague group mainly defined via the preservation of parts of the parental infraciliature. The kahliellids preliminary comprise, besides the name-bearing type genus Kahliella, genera such as Parakahliella and its African pendant Afrokahliella or the monotypic Engelmanniella. In total 68 species distributed in 21 genera and subgenera are revised. As in the previous volumes almost all morphological, morphogenetic, molecular, faunistic, and ecological data, scattered in almost 700 papers, are compiled so that the four volumes (Oxytrichidae, Urostyloidea, Amphisiellidae and Trachelostylidae, Gonostomatidae and Kahliellida) provide a detailed insight into the biology of almost 500 species of hypotrichs. The series is an up-to-date overview about this highly interesting taxon of spirotrichous ciliates mainly addressed to taxonomists, cell biologists, ecologists, molecular biologists, and practitioners.

The present book is a monograph about two groups of hypotrichous ciliates, namely the Amphisiellidae and the Trachelostylidae. It is the third of six volumes which - view the Hypotricha, one of the three major taxa of the spirotrichs. The first volume is about the Oxytrichidae, a rather large group, many species of which have 18 highly characteristically arranged frontal-ventral-transverse cirri and, much more importantly, a comparatively complex dorsal ciliature due to (oxytrichid) fragmen- tion of dorsal kineties during cell division (Berger 1999). The second volume deals with the Urostyloidea, which are characterised by a zigzag-arrangement of the ventral cirri (Berger 2006). Although this pattern is often very impressive, it is a relatively simple feature originating by a more or less distinct increase of the number of frontal-ventral-transverse cirri anlagen. These anlagen produce cirral pairs which are serially arranged in non-dividing specimens. Some - ers are likely astonished that the monograph on urostyloids does not include Urol- tus, a group of tailed species, which also have a distinct zigzagging cirral pattern. However, morphological and molecular data indicate that the zigzag pattern of U- leptus evolved independently, that is, convergently to that of the urostyloids. Thus, Uroleptus was excluded from the urostyloid review. A zigzag pattern is also known from some oxytrichids, for example, Neokeronopsis, Territricha, Pattersoniella, showing that this pattern evolved several times independently (Berger 1999, 2006, Foissner et al. 2004).

The present book is a monograph about two groups of hypotrichous ciliates, namely the Amphisiellidae and the Trachelostylidae. It is the third of six volumes which - view the Hypotricha, one of the three major taxa of the spirotrichs. The first volume is about the Oxytrichidae, a rather large group, many species of which have 18 highly characteristically arranged frontal-ventral-transverse cirri and, much more importantly, a comparatively complex dorsal ciliature due to (oxytrichid) fragmen- tion of dorsal kineties during cell division (Berger 1999). The second volume deals with the Urostyloidea, which are characterised by a zigzag-arrangement of the ventral cirri (Berger 2006). Although this pattern is often very impressive, it is a relatively simple feature originating by a more or less distinct increase of the number of frontal-ventral-transverse cirri anlagen. These anlagen produce cirral pairs which are serially arranged in non-dividing specimens. Some - ers are likely astonished that the monograph on urostyloids does not include Urol- tus, a group of tailed species, which also have a distinct zigzagging cirral pattern. However, morphological and molecular data indicate that the zigzag pattern of U- leptus evolved independently, that is, convergently to that of the urostyloids. Thus, Uroleptus was excluded from the urostyloid review. A zigzag pattern is also known from some oxytrichids, for example, Neokeronopsis, Territricha, Pattersoniella, showing that this pattern evolved several times independently (Berger 1999, 2006, Foissner et al. 2004).

The present monograph is the fourth of six volumes which review the Hypotricha, a major group of the spirotrichs. The book is about the Gonostomatidae, the Kahliellidae, and some taxa of unknown position in the hypotrichs. Gonostomum was previously misclassified in the Oxytrichidae because its type species Gonostomum affine has basically an 18-cirri pattern, which is dominant in the oxytrichids. A new hypothesis, considering also molecular data, postulates that this 18-cirri pattern evolved in the last common ancestor of the hypotrichs and therefore it appears throughout the Hypotricha tree. The simple dorsal kinety pattern, composed of only three bipolar dorsal kineties, and gene sequence analyses strongly suggest that Gonostomum branches off rather early in the phylogenetic tree. Thus, the Gonostomatidae, previously synonymised with the oxytrichids, are reactivated to include the name-bearing type genus and other genera (e.g., Paragonostomum, Wallackia, Cladotricha) which have the characteristic gonostomatid oral apparatus. The Kahliellidae are a rather vague group mainly defined via the preservation of parts of the parental infraciliature. The kahliellids preliminary comprise, besides the name-bearing type genus Kahliella, genera such as Parakahliella and its African pendant Afrokahliella or the monotypic Engelmanniella. In total 68 species distributed in 21 genera and subgenera are revised. As in the previous volumes almost all morphological, morphogenetic, molecular, faunistic, and ecological data, scattered in almost 700 papers, are compiled so that the four volumes (Oxytrichidae, Urostyloidea, Amphisiellidae and Trachelostylidae, Gonostomatidae and Kahliellida) provide a detailed insight into the biology of almost 500 species of hypotrichs. The series is an up-to-date overview about this highly interesting taxon of spirotrichous ciliates mainly addressed to taxonomists, cell biologists, ecologists, molecular biologists, and practitioners.