MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 273 



the long axis much like any other flagellate; shelled forms, like 

 Ceratium, have a more involved division process by reason of the 

 hard covering of plates. Here the division plane passes through the 

 sutures between certain definite plates (Fig. 131). The daughter 

 cells in some cases remain attached to form peculiar and character- 

 istic catenoid colonies and the peculiar form Polykrikos is regarded 

 as such a colony which has become permanent (Fig. 132). Division 





'/'S 



0': 



B 



Fig. 132. — Polykrikos schwartzi and development of its nematocysts. 

 (After Chatton.) 



in resting phases differs according to the species and varies in 

 permanent and temporary resting conditions; sometimes it occurs 

 within the parent shell, in other cases the outer shell is discarded 

 before division. 



Multiple division is widespread especially in quiescent reproduc- 

 tive forms protected by gelatinous membranes or cysts; the latter 

 are sometimes drawn out into peculiar crescentic capsules within 

 which the individual divides to form several products. Gymnndi- 

 18 



