264 BIOLOGY OF THE PROTOZOA 



the reorganization of the protoplasm or a restoration to a labile and 

 undifferentiated condition. Other evidences of de-differentiation 

 are shown by the loss through absorption of the old membranelles, 

 cirri, undulating membranes, oral baskets of the Chlamydodontidae 

 and kinetic elements of different kinds (see Chapter VI) while new 

 elements replacing them are developed from the protoplasm. In 

 this way there is a more or less complete reconstruction or reorgan- 

 ization of the organization at each division. (See also Herzfeld, 

 1925, and Schmahl, 1926.) 



Another characteristic evidence of inter-divisional differentiation 

 is shown by the polarization of the cell immediately prior to divi- 

 sion whereby "division zones" are set up through which division of 

 the cell takes place. Such division zones first described by Popoff 

 (1907) are quite evident morphologically in Frontonia leucas and 

 physiologically in Paramecium caudatum or Uronychia transfuga 

 (Fig. 136). Paramecium caudatum when cut near the anterior or 

 posterior end, as indicated in Fig. 136, does not regenerate the lost 

 part (Calkins, 1911; Peebles, 1912). A membrane is formed over 

 the cut surface and cortical differentiations in the form of coordinat- 

 ing fibrils, basal bodies, cilia and trichocysts are produced. The 

 result is a characteristic truncated cell. When this divides, division 

 occurs in the geometrical center of the organism as it was before 

 cutting and not in the center of the truncated cell (Fig. 136, 3c). 

 Two diverse cells result from division; one is normal and full-sized, 

 the other small and truncated. It very often happens that cutting 

 in this manner induces deep-seated changes in the organization and 

 such that the precision of division phenomena in the truncated cell 

 is destroyed and incompletely divided cells or monsters result. 

 (Such a monster, one with 16 mouths, is illustrated in Fig. 136, o). 

 See also Herzfeld (1925) on the occurrence of abnormalities and 

 monsters in Paramecium. Similar monsters may be produced 

 experimentallv by use of drugs (e. q., KCN) as shown by de Garis 

 (1927). 



Still further evidence of inter-divisional differentiation is shown 

 by the antecedent nuclear changes preparatory to division whereby, 

 in ciliates, macronuclear elements discard part of their substance 

 into the cytoplasm and fuse to form a single, usually ellipsoidal 

 macronucleus which then divides (Uronychia, Stentor, Uroleptus, 

 Spirostomum, etc.). Or in flagellates the entire kinetic complex is 

 absorbed in Lophomonas and several other types of flagellates (see 

 Chapter VI). 



It thus appears that well-marked changes of the nature of differ- 

 entiations in the organization are taking place during the inter- 

 divisional metabolic period, and that transformations of the nature 

 of de-differentiations whereby the protoplasm is restored to the 

 labile condition of a young organism occur with each division of 



