1919] Rhodes: Binary Fission in Collodictyon triciliatum Carter 245 



idiochromatin. Such a distinction in this instance is, however, more 

 physiological than morphological. 



Conceived in such a category, Collodictyon may stand closely 

 related to the parasitic flagellates containing a parabasal body (kineto- 

 nucleus of Hartmann). This would emphasize the fact that Hart- 

 mann 's Binucleata is based upon a fundamentally physiological rather 

 than a true morphological character. The macrokaryosome, through 

 the changing metabolic equilibrium, brought about by change from a 

 free living to a parasitic mode of life, might be preserved and persist 

 as a result of purely chemical reaction, thus becoming the parabasal 

 body. This possible origin of the parabasal body is purely theoretical. 

 Rhynochonionas (Belar, 1916) and Bodo caudatus (Alexeieff, 1911a), 

 as far as I know, are the only free living flagellates having any per- 

 sistent character comparable to a parabasal body. The fact that the 

 parabasal body is not present in all parasitic flagellates, nor constant 

 in the life-history of some, would emphasize its dependence upon 

 chemical nucleo-cytoplasmic equilibrium and its probable origin from 

 a primitive condition such as is found in Collodictyon. 



Werbitsky's work (1910), in which, by feeding host rats para- 

 fuchsin, tryparosin or oxazine, the parabasal body was dissolved and a 

 strain of parasites obtained in which this body did not appear through 

 several successive generations, may be similarly interpreted. Anything 

 tending to counterbalance or upset the metabolic equilibrium of the 

 cell would be expected so to affect a simple passive mass of chromatin 

 which no longer functions in its original role, but persists as a surplus 

 or reserve. Since chromatin seems to be the substance in which meta- 

 bolism centers, the parabasal body would thus probably function as a 

 kinetic reservoir for the motor activities of the cell. Evidence from 

 Collodictyon emphasizes this interpretation of Kofoid and Swezy 

 (1915). 



Mitosis in Metazoa is variable in its details, but as found in the 

 Protozoa it is variable in its fundamental features, so much so that 

 it may be classified into categories. Little distinction was made in the 

 types of mitosis until Nagler (1909, p. 46) designated what had pre- 

 viously been called amitosis in Amoeba and many Protozoa as "pro- 

 mitosis" in contrast to the type of mitosis as found in Metazoa and 

 Metaphyta. "Fur die sogannte Amitose der Protozoen fuhrt man 

 daher am besten eine neue Bezeichnung ein und definiert sie als eine 

 Kernteilung, die weder ausgesprochene Mitose, noch Amitose ist und 

 sich charakterisiert durch die Teilung eines Nucleocentrosoms, des 

 Caryosoms. Ich schlage deshalb fur diese Teilungsform den Namen 



