520 Harper. — Cell- Division in Sporangia and Asci. 
substances are entirely distinct in their origin and consistency. 
The presence of epiplasm is a necessary result of the peculiar 
method of cutting out the daughter cells in the ascus, and 
together with this, may be taken as a criterion for distinguish- 
ing asci in every case. From this standpoint the ascus appears 
so far as yet known as a new structure, characteristic of the 
group of the Ascomycetes. By this I would by no means 
say that the process of cutting out the spores by free cell- 
formation as I have described it, may not have been developed 
from some other method of cell-division. Investigation of 
the method of spore-formation in such forms as Exoascus , 
Dipodascus , and Eremascus may perhaps throw further light 
on the matter. For the present the peculiar phenomena 
observed by Strasburger 1 in the swarm-spore formation in 
Oedogonium may be regarded as possibly analogous to and 
indicating a possible origin of the process in the ascus. 
Strasburger found that in a cell of Oedogonium which is about 
to form a swarm-spore, a hyaloplasmic-mouthpiece appears 
on the side of the cell-body, and that the nucleus, which up 
to this time may have been in any part of the cell, migrates 
to a position just beneath this mouthpiece. Rays now appear 
in the protoplasm at the base of the mouthpiece, and extend 
back into the protoplasm of the cell. The cilia also begin 
to bud out around the base of the mouthpiece. The cell- 
body now rounds up more and more to form the swarm- 
spore, which may be enclosed in a thin vesicle, when it 
escapes from the mother cell. Strasburger believes that this 
vesicle here, and in other cases of swarm-spore-formation, 
represents the cast off plasma-membrane of the mother cell. 
How the new plasma-membrane of the swarm-spore is formed 
is not certain. It is probable that the hyaloplasmic mouth- 
piece is a centre of formative activity at this stage. The 
migration of the nucleus to this region reminds one of what 
Haberlandt has found as to the position of the nucleus in 
cells whose walls are being thickened on one side. Haberlandt 
concludes that the nucleus is directly concerned in the forma- 
1 Zellbildung u. Zelltheilung, 3. Aufl. 
