No. 3] THE PROTOZOA AND METAZOA. 75 1 



the "nucleolus-centrosome " of Eiiglena, for the latter is 

 "achromatic" and probably equivalent to the pole-plates of 

 Spirochona. 



A very similar description has been given in the case of 

 another parasitic ciliate, Kentrochona Ncbaliac. According to 

 Rompel's ('94) description, the nucleus of Kentrochona develops 

 at one pole an "achromatic" mass, which extends outwards 

 and bears two centrosomes at its extremity. After this mass 

 is well developed a similar structure appears at the opposite 

 pole. 



Rompel then proceeds as follows: " Wie wird der Gegenpol gebildet ? 

 Genauer, in welchem Lageverhaltniss stehen Chromatin und Kernspindel 

 (achromatic portion) wahrend der AusbUdung des Gegenpols ? Nach den 

 vorliegenden Praparaten diirften iiberhaupt nur zwei Mbglichkeiten in 

 Betracht kommen. Entweder wird das von Anfang an ring- oder cylinder- 

 formige Chromatin von der Kernspindel central durchbohrt, und diese wird 

 so zur Achse des Chromatinhohlcylinders, oder die Kernspindel zieht sich 

 unter dem ventral eingebuchteten Chromatinhohlcylinder her." Rompel's 

 Fig. 4 e represents the latter alternative, which certainly suggests the action 

 of thesphere in Noctilucaj ioxm Kentrochona the "achromatic Kernspindel," 

 like the ^'central-spindle " of Noctiluca, is apparently sunk in the nucleus 

 and stretches from pole to pole. 



Rompel's account of the division of Kentrochona is very 

 faulty, and the different stages described are separated by wide 

 gaps. His "centrosomes," too, have been questioned by Hert- 

 wig ('96), Balbiani ('94), Flemming ('94), and others, most of 

 whom think he has mistaken micronuclei for centrosomes. 

 Their criticisms are upheld by Doflein ('96, '97), who has recently 

 reexamined mitosis in Kentrochona. According to him the 

 process of division is very similar to that of Spirochona. 



" Die Theilung des Hauptkerns stammt in den grossen Ziigen mit derjeni- 

 gen bei Spirochona iiberein, wie sie besonders eingehend R. Hertwig und 

 Balbiani geschildert haben " (p. 363). The chromatin is sharply defined 

 against the achromatin which " in seitlicher Ansicht erscheint sie als 

 Anlage der Polplatte " (p. 364). 



Doflein mentions a distinct granule in the pole-plate during 

 the metaphase, which must be analogous to the so-called 

 "nucleolus" or "centrosome" of Spirochona according to 

 Balbiani. 



