SEXUALITY 703 



SIGNIFICANCE OF THE DIVERSITIES BETWEEN CONJUGANTS AND BE- 

 TWEEN GAMETE NUCLEI 



There is great diversity of opinion regarding the significance of the 

 observed differences between conjugants and between gamete nuclei. 

 This is due partly to the variety and complexity of the observed phenom- 

 ena, and partly to confusion as to the meaning of the concepts employed, 

 particularly concepts developed primarily with relation to phenomena in 

 higher organisms. An attempt will be made to summarize the more 

 prominent views concerning the main types of observed relations and 

 to set forth some general considerations concerning them. 



In some ciliates, the Vorticellidae and a few others, in which the 

 conjugants are always morphologically diverse and the gamete nuclei 

 morphologically alike, with fertilization of only the larger conjugant, it 

 is usually agreed that the conjugants differ sexually. Further, the gamete 

 nuclei in each conjugant are sometimes said to be of the same sex as the 

 conjugant. Some authors hold that the sexes here are female and male. 



In Chilodonella (see p. 689), in which the conjugants become 

 morphologically diverse during conjugation and fertilization is recip- 

 rocal, Enriques (1908) concluded that although both conjugants were 

 functionally hermaphroditic (producing two sexually diverse gamete 

 nuclei), the conjugants also showed a partial, incompletely developed 

 sex diversity, for which he devised the term "hemisexes." 



In Opisthotrkhum (see p. 689) fertilization is also reciprocal, 

 involving gamete nuclei with strongly marked morphological sex dif- 

 ferences. Nevertheless, in a majority of the conjugant pairs, the two 

 members diflfer in size. When the two are alike in size, both are large. 

 Dogiel (1925) interprets these facts as follows: the conjugants are all 

 functionally hermaphroditic, each producing male and female gamete 

 nuclei; but the conjugants also show the beginnings of sexual differentia- 

 tion, the small ones being more differentiated, for they can mate only 

 with large individuals, while the large ones can mate either with small or 

 large, though more commonly with the former. The small conjugants are 

 viewed as considerably differentiated toward the male condition, in spite 

 of their functional hermaphroditism. 



In Paramecium and Euplotes, fertilization is reciprocal, the gamete 

 nuclei show little or no morphological difference, and the conjugants 



