An Aspect of Morphogenesis in the Ciliate Protozoa*

SYNOPSIS. Stomatogenesis or new mouth formation sensu lato repnts an explicit example of a major morphogenetic phenomenon le life cycle of most ciliate Protozoa. Investigations of the process a number of approaches may yield data of considerable value. The present paper 3 such approaches are treated in some detail. udies of stomatogenesis can be of importance in providing addial information of significance on the structure and physiology a given organism. Five major types or categories of stomatoesis in ciliates are recognized. These are defined and discussed. search related to such an intrinsic value of the phenomenon the K carried out is generally only descriptive, and the most importechnic employed is some method of silver impregnation. a comparative approach is used, then attention may be focused possible homolegies in stomatogenesis as it occurs in diverse ies of ciliates. Such data are (or potentially are) of value not in the practical taxonomy of the organisms involved but also onsideration of phylogenetic and evolutionary interrelationships ing the higher groups comprising the entire subphylum Ciliophora. Such application of comparative studies may well become a very fruitful approach to certain problems in ciliate phylogeny; 2 examples are discussed briefly. Silver impregnation technics are again indispensable. Perhaps stomatogenesis will prove most valuable in the hands of developmental biologists who are seeking to solve 2 of the most intriguing problems in cell biology today: the exact origin of new kinetosomes (or centrioles), and their precise morphogenetic role in the life cycle of a cell or unicellular organism. Since this third approach to the study of stomatogenesis is of necessity a dynamic one, the researcher must employ sophisticated experimental technics to obtain data at the molecular and macromolecular levels of both organization and function. Some progress in this area has already been made, but the availability of “ideal” organisms has perhaps not been as widely realized as it should. Certain of the “higher” ciliates have a mode of stomatogenesis which would lend itself beautifully to fruitful investigation of problems concerning both replication or neoformation of kinetosomes and their possible role in fibrillogenesis in unicellular organisms.