CorpELAND: THE CONJUGATION OF SPIROGYRA CRASSA 1638 
conjugation when the wall between the tubes is absorbed: in all 
of it, in this stage and somewhat earlier, the nucleus was very con- 
stantly to be found close to the outer wall on the side opposite the 
conjugating tube. This could be seen in almost every conjugating 
cell. In the cells which failed to find mates the nucleus was more 
often invisible or obscured ; but sometimes it was very evident, as in 
the cell drawn. In this position the nucleus is rather smaller and 
much less conspicuous than in vegetative cells.* This position of the 
nucleus is the opposite of that usually assumed in cells with local- 
ized growth.t As is suggested in a recent paper by Miehe,f the 
central position of the nucleus in young and active cells, instead 
of a lateral one, even when growth is more or less localized, is 
easily understood in consideration of the various functions of the 
Nucleus. But this is the first instance known to me of a nucleus 
that moved to the opposite wall. This species, S. crassa, has 
been studied in the same connection by Gerassimoff,§ but not dur- 
ing conjugation, 
* Strasburger (Befructung und Zelltheilung, Jena, 5, 1878) says that early in 
the conjugation of S. guinina the nuclei become pale and disappear. 
t Haberlandt. Ueber die Beziehungen zwischen Function und Lage des Zell- 
kernes bei den Pflanzen. Jena, 1887. Physiologische Pflanzenanatomie. 2d Ed. 
23-24. 1896. 
t Ueber Wanderung des pflanzlichen Zellkernes, Flora, 88: 105-142. 1901. 
§ Ueber die Lage und die Function des Zellkernes. Moscow, 1900. 
