THE FUNDAMENTAL ORGANIZATION 63 



2. Endobasal Bodies With Centrioles. — Centrioles are kinetic ele- 

 ments in the form of minute granules, which in Metazoa and in 

 some types of Protozoa, form the focal points of the mitotic spindle. 

 In many Protozoa minute granules may be embedded in a matrix 

 of chromatin or plastin, or in a combination of both. These in some 

 cases form the poles of typical spindles, but in the majority of cases, 

 apart from the polar granules and the connecting centrodesmose, 

 there is little evidence of a typical spindle. 



In some forms this type of endosome undergoes changes in appear- 

 ance which Hartmann (1911) and his followers have interpreted as 

 periodic or cyclical in nature. Such variations have to do with 

 the concentration of the chromatin substance about the endobasal 

 body or centriole, being massive and dense in certain phases and 

 distributed in others. In Endamoeba dysenteriae the centriole in 

 the latter phase is distinct and definite but in the former phase it is 

 hidden by the dense chromatin (Fig. 31). From such conditions 

 Hartmann infers that all massive types contain hidden centrioles, 

 a conception applied by Naegler to all of the smaller amebae and 

 endamebae, but, according to Glaser, it is limited to comparatively 

 few types. 



Typical endobasal bodies in the form of centrioles are contained 

 in the first maturation nuclei of Vroleptus mobilis. Here each 

 massive micronucleus fragments into chromatin granules which 

 remain in a dense reticulum at one pole of the enlarging nucleus until 

 the chromosomes are formed. A centriole, hidden in this mass, 

 divides and one-half traverses the nucleus to form the first pole of 

 the maturation spindle but remains connected by a centrodesmose 

 with the other centriole which, in turn, forms the other pole of the 

 spindle (Fig. 32, b-g). Similar centrioles are found in widely 

 separated groups of Protozoa. In Coccidivm schubergi, according 

 to Schaudinn (1900), the endobasal body divides with a long con- 

 necting centrodesmose. Here, however, part of the material of 

 the centrodesmose collects into two granules with a more densely 

 stained connecting thread, thus producing a structure which Doflein 

 interprets as analogous to the mid-body (Zwischenkorper) of 

 Metazoa and plant cells. The fate of the centrioles after division 

 differs in different cases. In some, e. g., Bodo lacertae (Belaf, 1921, 

 Figs. 33, 34), they come from the nucleus and re-enter the daughter 

 nuclei; 1 in others they arise from basal bodies and become basal 

 bodies of the flagella after division (e. g., Chilomastix aulostomi, 

 Belaf, 1921; Spongomonas, Hartmann, etc.). 



While the embedding matrix in most of the above cases is similar 

 to chromatin in its reaction, and forms an important part of the 

 endobasal body, there are other types (e. g., My.vobolus pfeifferi, 



1 See, however, the earlier contradictory accounts of Prowazek (1904), Alexeieff 

 (1914), and Kuczynski (1918). 



