142 GENERAL BIOLOGY 



it is called karyogamy. It is doubtful, however, if 

 pure karyogamy ever takes place. The total fusion 

 of gametes, in turn, may be of various degrees of 

 specialization, either between similar cells (isogamy) 

 or between cells of different sizes (anisogamy), 

 leading to the differentiation of sexually specialized 

 cells (oogamy). 



,-%: 





FIG. 54. Bui!" letts : 1 , normal " monad " ; 2, same in the semi-amoeboid 

 condition preparatory to conjugation; 3, two individuals in the process 

 of coalescence; 4. the resultant zygote; 5, a zygote whose protoplasmic 

 contents have divided into spores; 6, young monads escaping from the 

 sporocyst. (After Kent.) 



Total Conjugation. Isogamy. Even in the 

 " lowest " of the Protista, the generalized condition 

 in which two similar adults conjugate to produce 

 a zygote is very rare. In such a case, the entire 

 organism functions as a gamete. One of the most 

 primitive examples is Bodo lens. In this species, two 



