MORPHOLOGY AND TAXONOMY OF THE INFUSORIA 485 



is the chief method of reproduction among the Suctoria but also 

 occurs in the Chonotricha (Spirochona, etc.). In Suctoria, budding 

 is either external or internal, in the latter case the budding area is 

 invaginated, the margins close over, and a brood chamber is formed 

 from which the embryos escape when formed. 



Multiple division or sporulation is also uncommon in the Ciliata, 

 but occurs in some of the more generalized and in some parasitic 

 types. When it occurs it is usually under the protection of a 

 temporary cyst (Colpoda, Ichthyophthirius). 



Sexual processes are practically universal in the group and the 

 main features of the process are similar throughout. In most cases 

 fusion is temporary and pronuclei are exchanged after which the 

 conjugants separate. In some cases, Vorticellidae, fusion is per- 

 manent and sexual dimorphism is the rule, in other cases such 

 dimorphism is expressed by the pronuclei, but in most cases there is 



Fig. 200.- 



-Glmicoma (DaUasia) frontata. Successive stages Leading to the formation 

 of copulating isogametes. (After Calkins and Bowling.) 



no sex differentiation whatsoever (see Chapter VIII). In Trachelo- 

 cerca phoenicopterus, Ichthyophthirius multifilius, Glaucoma (Dal- 

 lasia) frontata and in Opalinidae the fertilization phenomena do not 

 follow the usual routine of other ciliates, microgametes being formed 

 and fusion being permanent. 



Glaucoma (DaUasia) frontata illustrates a most unusual sexual 

 phenomenon. Here there are two types of fertilization, one by the 

 fusion of gametes, the other by typical conjugation (Figs. 200, 201 ). 



Conjugation always results in physical reorganization of the pro- 

 toplasm, the old macronucleus is broken up and the fragments are 

 absorbed in the cytoplasm, while a new macronucleus and new micro- 

 nuclei are differentiated from products of the first or second division 

 of the amphinucleus after fertilization (see Chapter VIII) . A similar 

 reorganization takes place at regular intervals of thirty days (P. 

 aurelia) or sixty days (P. caudatum) according to Woodruff and 



