182 



PROTOZOOLOGY 



the most complete information was obtained by Moewus through 

 his extended studies of certain Phytomonadina. In Polytoma (p. 

 222), Chlamydomonas (p. 217), and allied forms, the motile indi- 

 viduals are usually haploid. Two such individuals (gametes) fuse 

 with each other and produce a diploid zygote which becomes en- 

 cysted. The zygote later undergoes at least two divisions within 

 the cyst wall, in the first division of which chromosome reduction 

 takes place. These swarmers when set free become trophozoites and 



Fig. 86. Chilodonella uncinata (MacDougall). a, b, ventral and side 

 view of normal individual; c, d, ventral and side view of the tailed mutant. 



multiply asexually by division for many generations, the descend- 

 ants of each s warmer giving rise to a clone. 



Moewus (1935) demonstrated the segregation and independent as- 

 sortment of factors by hybridization of Polytoma. He used two va- 

 rieties each of two species: P. uvella and P. pascheri, both of which 

 possess 8 haploid chromosomes. Their constitutions were as follows: 



P. uvella 



Form A: Oval (F), without papilla (p), with stigma (S), large (D) 



(Fig. 87, a). 

 Form B: Oval (F), without papilla (p), without stigma (s), large (D) 



(Fig. 87, 6). 



P. pascheri 



Form C: Pyriform (f), with papilla (P), without stigma (s), large 



(D)(Fig.87,c). 

 Form D: Pyriform (f), with papilla (P), without stigma (s), small 



(d)(Fig.87,6;). 



