1904 | HOLFERTY; ARCHEGONIUM OF MNIUM 117 
fertilization taken place. There are two ways in which this 
phenomenon can be accounted for: first, the central cell may 
have divided very early, giving rise to two central cells, each of 
which later divided and gave rise to an egg and ventral canal 
cell; second, the lowest canal initial may have acted as a central 
cell, producing by its division an egg and ventral canal cell. 
Coker (22, p. 137) has reported and figured a similar case in 
Mnium, and regards the supernumerary egg as derived from the 
lower neck canal cell. The absence of septa is to be noted in 
each instance, a condition not infrequent in gymnosperms. 
Campbell (14) figures an archegonium of Geothallus which 
apparently had cut off successively two ventral canal cells, and 
there is no wall separating the second cell from the egg. There 
is here the possibility that the two ventral canal cells may be the 
result of a division of the original ventral canal cell instead of 
successive divisions of the egg. This view is suggested by the 
position of the nuclei of the ventral canal cells, both of which 
are in contact with the septum. 
We are disposed to attribute the vigor and consequent 
supremacy and potency of the egg in bryophytes, just as we do 
that of the lowest megaspore in angiosperms, to the advantages 
of nutrition, that is, it is the cell nearest the source of supply. 
It would be an interesting problem to determine whether by 
nourishing the canal cells and starving the egg the former could 
be made to assume the function of the latter. Figs. g2 and 43, 
as also the case in Marchantia noted, seem to suggest that they 
could do so. At least it is clear from the illustrations here given 
that there is more or less fluctuation in the origin and work of 
the cells of the row, and that under certain conditions other 
closely related cells may do the work of the egg. The cases 
enumerated seem to furnish sufficient evidence to support the 
view that the cells of the row are homologous. 
3. Homology of the axial series and sperm mother-cells.—Another 
line of evidence indicating the homology of archegonia and 
antheridia is offered by a number of abnormal forms that con- 
stitute a series lying between normal archegonia and antheridia. 
Bisexual organs are by no means rare. That egg and sperms can 
