FAULT: DEVELOPMENT OF ASCUS. 
105 
is to be enquired if the sporogenesis of such a sporangium could not 
be homologized with that of the ascus, or in other words if the 
ascus might not find its ancestor in a Saprolegniineous zoospor- 
angium. If so, then we may with more reason look for the ances¬ 
tors of the Ascomycetes among the lower fungi. There are, of 
course, marked differences in the sporogenesis of zoosporangium 
and ascus, but that is to be expected,—they exist between even 
the sporangia of Saprolegnia and Mucor, which are with little 
doubt rather closely alliecl, — for if the Ascomycetes be connected 
phylogenetically with the Saprolegniineae they are removed at a 
great distance as is shown by the characters of their vegetative 
bodies and organs of reproduction, differences which, it is needless 
to say, have arisen through the acquirement of very different habits. 
But these differences may not be found to be irreconcilable with a 
theory that connects the two phylogenetically. For instance, a 
most striking difference is the fact that the sporangium is multinu- 
cleate from the beginning while the ascus starts in a binucleate con¬ 
dition ; but this might be accounted for without difficulty if it is 
granted that a septate thallus, the cells of which are one- to few- 
nucleated, may arise from a coenocvtic thallus. Likewise it will be 
found that other differences are not so formidable as they appear at 
first sight, and that taken with the similarities they may not be such 
as to debar connecting the one with the other. 
In the preparations leading to the formation of the spores there 
are two phenomena which in general are the same in both the 
zoosporangium and the ascus, and which may not be without signi¬ 
ficance : (1) the differentiation of the protoplasm into dense and 
vacuolated portions, (2) the migration of the nuclei to a peripheral 
position in the dense protoplasm. In regard to the differentiation 
of the protoplasm, it is worthy of note in this connection that in the 
ascus, vacuoles frequently occur in a more or less central position 
directly following the last nuclear division. Harper (’99) noted 
these vacuoles in Lachnea, but ascribed them to the escape of 
nuclear sap in the anaphase stages of the last mitosis. This expla¬ 
nation does not seem adequate, however, to account in many cases 
for the size, number, and position of all of them, even if it be 
granted that the escape of nuclear sap might be responsible for 
some. 
From this point on, the processes are apparently much more 
