SEXUAL PHENOMENA IX THE PROTOZOA 



227 



Under certain conditions some of the adult cells become separated 

 from the colony and pass into a resting state, during which they divide 

 into eight biflagellated microgametes, and these, as soon as liberated, 

 conjugate in pairs (Hieronymous, Rostafinski, '75). There is no size 

 differentiation between the conjugating microgametes. Nor is there 



Fig. 125. — Gonium pectorals O. F. M., in division. 

 The third cleavage results in two layers of four cells (z, k, o). The flattening occurs in the 

 12-16-cell stage (g, m,p). 



in the somewhat better-known form, Pandorina morum. In the latter, 

 which is also a sixteen-cell colony, after a certain number of asexual 

 generations, a generation appears in which each of the sixteen cells 

 divides, not into sixteen parts for a new colony, but as in Gonium into 

 eight gametes, which ultimately become free, conjugate, and pass into 

 a resting zygote condition. After a longer or shorter period, either 

 the cyst bursts, and a naked individual emerges, which by division 



