C2DOGONIUM. 89 
have been evolved; but in Volvox the insertion of the cilia has under- 
gone a lateral displacement, so that they now spring from the base of 
the mouth-piece. 
The large egg-cells, although not escaping from the mother colony 
into the surrounding water before fecundation, are in a measure free 
to move passively within the mother colony. The same kind of 
stimulus operative in bringing the eggs and spermatozoids together in 
Fucus may in all probability obtain also in Volvox. In the case of 
dicecious forms especially, investigation along this line will probably 
yield important results, and with modern technique a careful study of 
the behavior of the sexual nuclei and other cytological details of fecun- 
dation, concerning which we know practically nothing, will also bring 
to light much of value and interest to our knowledge of fecundation. 
GEDOGONIUM. 
We shall now pass to the consideration of the sexual process in 
certain of those fresh-water alge in which the female gamete remains 
enclosed in its more specialized and characteristic organ, the odgonium. 
Beginning with such forms as Cylindrocapsa and Gidogonium we 
have a progressive series of forms culminating in Coleochete, in which, 
apart from the specialized bisexual products, there are more highly 
differentiated and characteristic sexual organs. 
The nature and development of the sexual organs in @dogonium 
and the process of fecundation have been carefully described by Pring- 
sheim (’56) and others in so far as these phenomena may be followed 
with accuracy in the living material, but, as regards the more minute 
structure of the spermatozoid and egg-cell and the behavior of the 
sexual nuclei in fecundation, the researches of earlier observers leave 
much to be desired. In more recent years Klebahn (’91) has suc- 
ceeded in filling in many of the gaps, and it is to his investigations 
that we are chiefly indebted for a more detailed knowledge of the 
behavior of the nuclei. 
When the odgonium (@dogonium bosctz) has attained its defini- 
tive form, the protoplasm, which encloses a large vacuole, is every- 
where closely applied to the cell-wall. Changes which lead to the 
formation of the opening in the upper part of the organ are then 
manifested. Near the spot at which the odégonium will open a small 
elliptical lamella is formed, which gives a cellulose reaction. The 
formation of the lamella proceeds from a colorless portion of the cyto- 
plasm, which can not be distinguished at an earlier stage. Between 
cell-wall and lamella a lens-shaped cavity arises, and a transverse slit 
