58 Reproduction and Life-Cycles 



The stigma divides in Chlamydomonas nasuta (140), whereas the old 

 stigma passes to one daughter flagellate in Platydorma caudata (228). 

 Division of the chroma tophores has been reported in certain Euglenida 

 (115). Division of pyrenoids has been described in Eudorina illinoisiensis 

 (117); resorption of the old pyrenoid and differentiation of new ones occur 

 in Chlamydomonas nasuta (140). 



Flagella probably do not split in fission and the few reports of such 

 a process are based upon inadequate evidence. Retention of the old 

 flagella has been described most frequently. In biflagellate and multi- 

 flagellate species, each daughter organism may receive one or more of the 

 original flagella and develop the necessary new ones, as in Heteronema 

 (163) and Trichonympha (152). However, flagellar resorption occurs in 

 Monas (210) and in Phytomonadida which divide within a parental theca. 

 The old flagella and associated structures also degenerate in Lophomonas 

 and related genera (Fig. 2. 2, L). The axostyle of trichomonad flagellates, 

 the pharyngeal-rod apparatus of Heteronema (163), the siphon of Ento- 

 siphon (115), and the cresta of devescovinid flagellates (152) undergo 

 resorption, whereas the costa of trichomonads apparently is retained by 

 one of the daughter flagellates. The kinetoplast of Trypanosomidae di- 

 vides but parabasal bodies of other flagellates usually do not. One of 

 the exceptions is Cliilomonas Paramecium in which each daughter re- 

 ceives part of the old parabasal apparatus (115). Parabasal bodies are 

 sometimes retained intact, as in Barbulanympha laurabuda (66); or partial 

 or complete resorption may occur. Although complete resorption of the 

 parabasal body sometimes occurs in Trichoynonas termopsldis and various 

 devescovinid flagellates, a portion often remains attached to its blepharo- 

 plast. In these cases, the parabasal of one daughter is regenerated from the 

 persisting fragment while that of the other is differentiated de novo (152). 



The rigid theca of Ceratiiim (Fig. 2. 2, A-G) and related dinoflagellates 

 is divided in fission and the missing portions are regenerated. On the 

 other hand, such testate flagellates as Trachelomonas volvocina usually 

 undergo fission within the test, one daughter emerging to produce a new 

 test (99). 



The simpler Sarcodina often show little of cytological interest aside 

 from division of the nucleus. However, the cytoplasmic changes in 

 Amoeba proteus (39, 162) indicate that the physical aspects of fission are 

 not particularly simple (Fig. 2. 3, A-C). The presence of a shell compli- 

 cates reproduction of many Sarcodina. In primitive genera {Cochlio- 

 podium, Pseudodiffliigia), the simple test is divided in fission. Euglypha 

 alveolata secretes reserve shell-plates and stores them (Fig. 2. 3, D) until 

 the next fission, when they are passed to one of the daughter organisms. 

 The other retains the old test. In typical Foraminiferida, schizogony has 

 replaced binary fission. 



Fission in ciliates is typically transverse (Fig. 2. 4, H) and, in at least 



