DERIVED ORGANIZATION 



119 



m- 



Muniz, 192S). Lwoff (1931) finds that this nucleal reaction is 

 confined to a cortical zone of the body in question, and holds that 

 probably in all cases the so-called kinetonucleus is composed of 

 two quite different substances, one of which, the medullary sub- 

 stance according to the observations of Grasse (1926), is apparently 

 of lipoid nature. Lwoff (1931) gives a new interpretation of para- 

 basals and kinetonuclei in the simpler parasitic flagellates such as 

 Leptomonas ctenocephali (Fig. 65). Here the so-called "parabasal 

 filament" (p.f.) does not originate from 

 the blepharoplast ("mastigosome" of Lwoff 

 = m) but from a flagellar ring (r) quite re- 

 moved from and not connected with the 

 blepharoplast. The latter, however, gives 

 rise to and is connected with what he terms 

 the "kinetonucleus," which he shows has 

 a chromatin cortex (k). The latter gives 

 rise to still another element which he calls 

 the "paranuclear" body (c.Bin). In this 

 case the "parabasal" is not derived from 

 the blepharoplast, but is of entirely differ- 

 ent origin from parabasals of other forms. 

 What Lwoff calls the "kinetonucleus" has 

 the same relation to the blepharoplast as 

 do the majority of parabasals (e. g., 

 Crithidia, Trypanosoma cruzi, etc., Fig. 61). 

 Further study of these perplexing fibrils in 

 flagellates and particularly in the hyper- 

 mastigida, must be made before the puzzle 

 of exact homologies can be solved. 



3. Other Cytoplasmic Kinetic Elements.— 

 A unique cytoplasmic kinetic element, ap- 

 parently homologous with the centrobleph- 

 aroplast of certain flagellates, is found 

 in some types of Heliozoa. The non-com- 

 mittal name central granule (Centralkorn) 

 was given to this structure by Grenadier 

 (1869), who was the first to observe it. 

 In some types it lies in the geometrical 



center of the cell (Acanthocystis aculeata, Sphaerastrumfockei, Raphi- 

 diophrys pallida, etc.) ; in other types it is ex centric (Dimorpha m utans, 

 Wagnerella borealis) or absent altogether (Actinophrys sol, Actino- 

 sphaerium eichhornii, Camptonema nutans, etc.). In the ordinary 

 vegetative activities of the cell, radiating fibers starting from the 

 central grain extend through the protoplasm to the periphery, where 

 they form the axial filaments of the pseudopodia (Fig. 66) . In division 

 stages of the cell, the central grain first divides forming an amphi- 



— I 



— k 



"c.Bm 



-p.f. 



Fig. 65. — Lepto m onas 

 ctenocephali. Parabasal ap- 

 paratus consisting of peri- 

 flagellar ring and posteriorly 

 directed filament; "kineto- 

 nucleus" and "mastigosome" 

 (basal body). (After A. and 

 M. Lwoff, Bull, biologique de 

 la France et de la Belgique, 

 courtesy of Prof. N. Caullery 

 and Les presses Universitaires 

 de France.) 



