Furchungsspindel im befruchteten Ei. 419 
Die Ansicht, dass die Pole der ersten Furchungsspindel als 
die Abkömmlinge der Spermastrahlung und ihrer Centriolen auf- 
zufassen sind, teilen gerade diejenigen Autoren, welche den Be- 
fruchtungsprozess zusammenfassend bearbeitet haben, so vor allem 
v. Erlanger, Wilson und Korschelt. 
Wilson betont gleichfalls, dass der Umstand, dass die 
Spermastrahlungen und Üentrosomen bei verschiedenen Tieren 
zeitweise schwinden, noch keinen Grund für die Wahrscheinlich- 
keit der Carnoy-Lebrunschen Hypothese bildet und keines- 
wegs zur Annahme der Entstehung der Centrosomen der ersten 
Furchungsspindel de novo zwingt. Er lässt die Auffassung von 
Sobotta, Mac Farland, Kostanecki, Co& zu Recht be- 
stehen, welche ‚„relying partly on the analogy of other forıns, partly 
on the occasional presence of the centrosomes during the ceritical 
stage, urge that the disappearance of the sperm-centrosomes 18 
due to the disappearance of the asters, which renders diffieult or 
impossible the identification of the centrosomes among the other 
protoplasmie granules of the egg.“ Er sieht eine Stütze für diese 
Ansicht in den Befunden bei Ascaris, Chaetopterus, Thalassema, 
bei denen in dem kritischen Stadium die Spermastrahlung nicht 
schwindet; in meinen Beobachtungen bei Physa und Coö&ös bei 
Cerebratulus sieht er eine Stütze dafür, dass: „even though the 
sperm-centrosomes disappear from view, there is some kind of 
genetic continuity between them and the cleavage-centrosomes“, 
of the cleavage-spindle. Then come the eggs of Toxopneustes (Wilson) 
and Thalassema (Griffin), where the spermasters appear early and develop 
to a very considerable size, but nevertheless become very much smaller and 
less conspieuous after the germ-nuclei have come together. After these we 
must place the eggs of Physa (Kostaneckiand Wierzejski), for here the sperm- 
asters, after becoming very large and conspicuous. degenerate to such an ex- 
tent that only a very few exceedingly delicate fibres remain. Those of Cere- 
bratulus follow next. Here the spermasters increase in size until they ex- 
tend throughout the whole body of the cell, but at the time of fusion of the 
germ-nuclei they degenerate completely. The peripheral portions of their 
fibres, however, may be followed, as stated above of Pleurophyllidia, Prosthe- 
ceraeus etc., where the spermasters degenerate soon after their formation, 
so that for a considerable period the egg is without trace of aster-fibres. 
Yet in all of those cases where the spermasters disappear and their centro- 
somes become lost among the other granules of the cell, we are justified in 
believing that the sperm-centrosomes nevertheless retain their identity, and 
later reappear in the cleavage-asters.“ 
