Cytologie und Befruchtung. 339 



Hautschicht. He considers that the radiations take an active 

 part in the Separation of the poles. 



In the second mitosis the origin of the achromatic struc- 

 ture and the centrosphere received special attention. Care is 

 taken not to confuse „centrosphere" with „centrosome". The 

 centrosphere consists of the same substance as the astral rays 

 and the spindle fibers. In some of the preparations figured the 

 sharply staining bodies in the centrosphere are not regarded 

 as centrosomes but either chance granules or cut ends of 

 astral rays. 



Antheridea from the initial cell to stages in which aboiit 

 thirty cells appeared in cross sections showed no centrosomes. 



in the germinating spore the centrosphere gives rise to 

 the rays, but the rays may contribute to the substance of the 

 centrosphere. He believes that there is a Streaming movement 

 in the rays. If the Streaming is toward the nucleus the centro- 

 spheres will enlarge, but if the current is reversed the centro- 

 spheres will climinish. This theory accounts satisfactorily for 

 the appearance and non appearance of centrospheres as well 

 as for the occasional appearance of granules in the centro- 

 spheres. 



The asters arise at opposite poles of the nucleus but not 

 simultaneously. The two asters do not arise from the division 

 of the first one. The rays of the aster do not penetrate the 

 Caps. In the second mitosis the polar radiations disappear at 

 the end of the prophase to reappear in the telephase. 



The nucleolus contributes material to the chromosomes and 

 to the spindle. 



In the third mitosis the asters are frequently absent. The 

 Caps have few radiations ore non at all. In later mitosis the 

 resemblance to the usual vegetative division becomes more and 

 more pronounced and asters and centrospheres are exceedingly 

 rare. 



The centrosome problem is thoroughly discussed, and the 

 conclusion is reached that centrosomes, centrospheres and 

 blepharoplasts, and their radiations, spindle fibers and cilia 

 are only different manifestations of kinoplasmic activity. in all 

 cases movement being the principal function 



W. j G. Land (Chicago). 



Ikeno, S., Beiträge zur Kenntniss der pflanzlichen 

 Spermatogenese: Die Spermatogenese von Mar- 

 chantia polymorpha. (Beihefte zum Botanischen Centralblatt. 

 Original-Arbeiten. Bd. XV. Heft 1. 1903. p. 65— 88. Taf. 3. 

 1 Textfig.) 

 Die Untersuchung der zur Bildung der Spermatiden führen- 

 den Theilungsvorgänge bei den Innenzellen der jungen Anthe- 

 ridien von Marchantia polymorpha ergab folgende Resultate: 

 Jede Innenzelle erscheint im Umriss annähernd viereckig und 

 ist, abgesehen von einer mehr oder minder grossen Anzahl von 



99* 



