160 



PROTOZOOLOGY 



Nyctotherus cordiformis (Fig. 79) takes place only among those 

 which live in the tadpoles undergoing metamorphosis (f-j). The 

 conjugants are said to be much smaller than the ordinary tropho- 



FiG. 79. The life-cycle of Nyctotherus cordiformis in Hyla versicolor 

 (Wichterman). a, a cyst; b, excystment in tadpole; c, d, division is 

 repeated until host metamorphoses; e, smaller preconjugant; f-j, con- 

 jugation; k, exconjugant; 1, amphinucleus divides into 2 nuclei, one micro- 

 nucleus and the other passes through the "spireme ball" stage before 

 developing into a macro nucleus; k-n, exconjugants found nearly exclu- 

 sively in recently transformed host; o, mature trophozoite; p-s, binary 

 fission stages; t, precystic stage. 



