THE PHYSIOLOGY OF FERTILIZATION IN CILIATES 3 2 1 



paramecin initiates activation tlirougli some other receptor than the 

 one operative in sexually induced activation. A thorough study of 

 the parthenogenetic action of paramecins is greatly to be desired, and 

 a systematic search for other agents with similar action should be 

 made. Since paramecin is a desoxyribonucleoprotein (van Wagten- 

 donk, 1948), other substances of this nature might well be investi- 

 gated. A study of the effect of parthenogenetic agents on blocked 

 stocks such as the CM stock should be particularly rewarding. 



As Metz and Foley (1949) suggest, these studies on partheno- 

 genesis in Faramecium have certain interesting implications for par- 

 thenogenesis in metazoa. The CM study shows that natural parthe- 

 nogenesis (natural autogamy) in Faramechivt and sexually induced 

 activation are initiated through different routes. This situation may 

 obtain in other forms, such as hymenopterous insects where the tgg 

 can develop either parthenogenetically or by sperm activation. Like- 

 wise artificial parthenogenetic agents need not necessarily act through 

 the same receptor as the sperm (Metz and Foley, 1949; Runnstrom, 

 1949). In fact, different parthenogenetic agents may act specifically 

 at different points in an activation chain, 



FERTILIZATION IN OTHER CILIATES 



Breeding systems containing clear-cut mating types have been 

 described in detail in only one form other than Paramecium, namely, 

 Euplotes patella. Mating types also occur in Leucophrys patula, Ony- 

 chodrovnis grandis, Stylonichia pustidata, and Loxophyllum fasciola 

 according to Jennings' (1939b) interpretation of Maupas' (1889) 

 observations. Recently mating types have been reported briefly in 

 Tetrahymeva (Elliott and Nanney, 1952; Elliott and Gruchy, 1952), 

 Stylojiicbia putrina (Downs, 1952) and Euplotes bar pa (Katashima, 

 1952). 



Abating types were first reported in Euplotes patella by Kimball 

 (1939). Subsequently Kimball (1941, 1942) and Powers (1943) 

 described the breeding system and inheritance of mating type in 

 greater detail. Kimball (1943) and Sonneborn (1947) have both 

 reviewed these studies extensively. Therefore, this discussion will be 

 confined primarily to a comparison of the physiology of fertilization 

 in Paramecimn and Euplotes. 



Kimball (1943) reports two (possibly three) non-interbreeding 



