76 BIOLOGY OF THE PROTOZOA 



witli nuclear dyes, especially with iron hematoxylin (Eiiglenida) ; in 

 other cases they stain feebly or not at all with the same dyes that 

 color the chromatin {e. g., Chilodon). In some cases they are large 

 and appear homogeneous throughout; in other cases there is a defi- 

 nite, deeply-staining central granule embedded in a more faintly 

 staining matrix, or such a granule may be present without the 

 accompanying matrix; or, finally, there is no evidence at all of kinetic 

 elements in resting nuclei, but collections of homogeneous substance 

 are present at the poles of the nucleus during division (pole plates) . 

 1. Large Homogeneous Endohasal Bodies. — In this type the endo- 

 basal body is conspicuous by its large size and homogeneous struc- 

 ture. It was first described by Keuten (1895) in Euglena viridis 

 and was early recognized as a kinetic element connected with nuclear 

 division as attested by the names intranuclear centrosome, division 

 center, etc., applied to it, while nuclei containing it were included 

 by Boveri in his "centronucleus" type. In Euglena viridis and 

 euglenoids generally, this endobasal body according to earlier 

 descriptions of Keuten, Tschenzoff (1916) and others, is the most 

 conspicuous structure of the nucleus, where, in the resting nucleus 

 it appears as a spherical or elongated ellipsoidal body with chromatin 

 granules of limited number suspended between it and the nuclear 

 membrane (Fig. 25, p. 62). It divides prior to division of the chro- 

 matin, first elongating with a concentration of its material at the 

 poles {B, C). The elongation continues until a thin fibril, called a 

 centrodesmose, alone connects the two halves (C, D). The centro- 

 desmose ultimately breaks and its substance is absorbed by the two 

 daughter elements (D). According to more recent observations 

 of Baker and of Hall (1923), however, there is an extranuclear ble- 

 pharoplast which divides with connecting paradesmose, the daughter 

 blepharoplasts as centrioles forming the poles of the spindle. (See 

 also Oxyrrhis, Fig. 43.) In the rhizopod Chlamydoyhrys stercorea, 

 as well as in the flagellate Bodo ovatus, the endobasal body which is 

 quite similar to that of Euglena, divides subsequently to division 

 of the chromatin (Schaudinn, Belar, Fig. 33), while in Amoeba 

 crystalligera (Schaudinn) there is no centrodesmose formed during 

 division, a condition not uncommon in the rhizopods {e. g., Arcella 

 milgaris according to Swarczewsky; Vahlkamfia liuiax (Fig. 26), and 

 many species of Endamoeha) . Not only is this simple type of endo- 

 basal body found in rhizopods and flagellates, but also in some cases 

 in the more complex ciliates, where, in Chilodon cucidlus, for example, 

 the macronucleus contains a definite endosome which behaves 

 exactly like that of Euglena (Fig. 34). It is highly probable that 

 in all of these cases the endobasal bodv is embedded in a core of 



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

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



