23 



gradually coarser and longer, and form the skein stage. Hand in hand 

 with this change, the cell body with its nucleus conspicuously enlarges 

 and attains a size double that of the first primary germ cell (»Ur- 

 samenzellen«), or larger. After the skein stage, the chromosomes pre- 

 sent a ring-like arrangement as Carnoy, Henking, vom R,ath etc. 

 have stated in other animals, each ring consisting of four round 

 chromosomes. With the appearance of the centrosome , the spindle 

 figure etc. they begin to divide. 



I may perhaps introduce here some remarks about the nucleolus, 

 the spindle fibre and the »Nebenkern«. 



As above described, the nucleolus is not homogeneous , but con- 

 sists of small granules. Before the division of the cell, granulation 

 becomes finer than before and finally disappears completely from the 

 nucleus at the exact time when the centrosome appears in the cell. This 

 behaviour of the nucleolus corresponds very well with the description 

 of O. Her twig who says: »Bei den Samenmutterzellen von Ascaris, 

 die mit schwachem Flemming' sehen Gemisch gehärtet sind, ver- 

 liert das Nuclein seine Färbbarkeit, während die Nucleolen in Säure- 

 fuchsin dunkelroth tingiert werden. Hier sah ich nun , daß in den 

 Vorbereitungsstadien der Nucleolus in mehrere Stücke zerfällt, daß von 

 diesen sich kleinste Kügelchen ablösen , daß solche hochroth gefärbte 

 Kügelchen sich auch auf den Kernfäden aufgelagert finden. Wenn 

 im weiteren Verlauf die Kernsegmente fertig angelegt sind und der 

 Nucleolus ganz verschwunden ist, dann sind erstens an der Oberfläche 

 des Kerns die Polkörperchen sichtbar geworden, und zweitens ist in 

 jedes Kernsegment ein dunkelroth gefärbtes Korn eingeschlossen, 

 das nach seinem Verhalten gegen Farbstoff'e wie Substanz des Nu- 

 cleolus aussieht.« Although I had not any opportunity to find out the 

 formation of the centrosome from the nucleolus as Wasielewski 

 and Brauer had, the coincidence in the time of the appearance of 

 the centrosome and the disappearance of the nucleolar substances 

 seems to indicate that there is some genetic connection between these 

 two bodies. 



Before the appearance of the centrosome a granulated spot occurs 

 in the cell protoplasm. This gradually elongates and forms a bundle 

 of fibrous matter. This seems to be the origin of the spindle fibre. 



The »Nebenkern« makes its appearance in the protoplasm stained 

 with Böhmer's Haematoxylin. Its structure is either granular or ho- 

 mogeneous. I can not say anything about its further changes. In the 

 germ cells of this zone, no yolk granule is seen. 



in. The Ripening zone. In this zone, the reduction of the chro- 

 mosomes takes place in the germ cells and form the spermatides of 



