84 BIOLOGY OF THE PROTOZOA 



the understanding that it involves no claim of finality, nor does it 

 indicate phylogenetic relationships. 



The kinetic structures most frequently found in the cytoplasm 

 of Protozoa are relatively simple, the more complex types which 

 have been revealed being found in comparatively few cases. In 

 considering Protozoa as a group, therefore, too much weight should 

 not be attributed to these more complicated forms. For purely 

 descriptive purposes they may be considered in the following order: 

 (1) Kinetic elements, which are morphologically and functionally 

 equivalent to intranuclear centrioles forming parts of endobasal 

 bodies and usually derived from them; (2) blepharoplasts equivalent 

 to basal bodies, or independent of basal bodies, which lie at or near 

 the bases of motile organoids and give rise to the kinetic structures 

 in them; (3) basal bodies derived from and independent of blepha- 

 roplasts; (4) parabasal bodies which are closely connected with the 

 blepharoplasts and probably derived from them; (5) centrodesmoses 

 and paradesmoses, or connecting fibrils between kinetic elements; 

 (6) rhizoplasts, or fibrils originating as outgrowths from the sub- 

 stance of specific kinetic elements and connecting two such elements 

 or ending blindly in the vicinity of the nucleus; (7) astrospheres 

 and centrosomes, similar to analogous structures in the cells of 

 Metazoa; (8) miscellaneous kinetic elements such as centroble- 

 pharoplasts, axostyles, parastyles and the neuromotor apparatus of 

 flagellates, "motorium," conductile fibrils, and mj^onemes of Infu- 

 soria, myophrisks of the Radiolaria, etc. 



Since many of these are characterized by their functional activi- 

 ties as well as by their specific structures, it is not illogical to find 

 that the same organoid performs generalized functions. Thus a 

 blepharoplast may be the same as a centriole, or as a basal body; 

 rhizoplasts may arise as a broken centrodesmose or paradesmose; a 

 myoneme as a conductile element, etc. The complexities of organi- 

 zation arise from the simultaneous presence of many of these differ- 

 ent kinetic elements in the cell where they may form a coordinating 

 system of organoids which Sharp and Kofoid have aptly designated 

 the neuromotor system. 



1. Blepharoplast, Basal Body and Centriole.— In many of the 

 comparatively simple Protozoa which have no specialized motile 

 organoids, the cytoplasm apparently lacks all traces of specific 

 kinetic elements. Thus in the entire group of Sporozoa, in the 

 simpler Gymnamoebida and in testate forms of rhizopods, kinetic 

 elements, if present at all, are in the form of endobasal bodies within 

 the nucleus or as centrosomes close to it. x\rndt (1924) however, 

 has recently described a centrosome, with centriole, which divides 

 and forms the poles of the mitotic figure in Hartmannella (Pseudo- 

 chlamysf) kUtzkei, a testate rhizopod (Fig. 41). In some of the 

 relatively simple rhizopods, however, especially those belonging to 



