Mating Substances 



and the Physiology of Fertilization 

 in Ciliates* 



CHARLES B. METZ,t Department of Zoology, 

 University of North Carolina, Chapel Hill 



In metazoan fertilization the egg and sperm meet, these two cells 

 adhere, the egg is activated, and the gametes fuse. Similarly, protozoan 

 fertilization involves an initial adhesion, a series of physiological and 

 morphological changes, and finally partial or complete cellular fusion. 

 It appears then that no profound physiological difference should 

 exist between the process of fertilization in metazoa and ciliate pro- 

 tozoa and that information regarding fertilization in these two groups 

 of organisms might profitably be considered together. Such an ap- 

 proach seems timely since much of the available information on ferti- 

 lization in ciliates (Kimball, 1943; Sonneborn, 1947, 1949; A4etz, 

 1948) and in metazoa (Tyler, 1941, 1948, 1949; Runnstrom, 1949; 

 Rostand, 1950; Rothschild, 1951a,b; Chang and Pincus, 1951; Bielig 

 and von Medem, 1949) has been reviewed extensively, but independ- 

 ently, in recent years. In keeping with this view certain problems in 

 the physiology of fertilization are outlined here, the methods em- 

 ployed to solve these are presented, and the degree to which these 

 efforts have succeeded is considered and compared. Since the review- 

 er's main thesis has developed from studies on Farimieciuni, the 

 physiology of fertilization in this form is discussed in some detail, 

 pertinent studies on other ciliates are then considered, and finally an 

 attempt is made to relate these investigations to metazoan fertilization. 



* The writer's studies were aided in part by grants from the National 

 Institutes of Health, U. S. PubHc Health Service, and from the American 

 Cancer Society. 



t Present address. Department of Zoology, Florida State University, Tal- 

 lahassee. 



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