Notes. 
573 
more complex if other additional modes of propagation appear, as 
they do in many Fungi. In Saprolegnia we can distinguish four 
kinds of propagation: (i) by simple mycelial growth, that is, by 
breaking of the mycelium into pieces ; (2) by zoospores ; (3) by 
oospores ; (4) by gemmae. The conditions for each of these four 
kinds of propagation are somewhat different, and it is thus possible, 
as my later investigations prove, to force the fungus at will into one 
or other of the four modes of propagation. 
The potentialities for the several kinds of propagation in the 
Thallophytes, such as Voucher ia , Oedogonium, Chlamydomonas, Sporo- 
dinia, Saprolegnia , Eurotium , &c., are quite equivalent, i.e. there 
is no cause in the inner nature of the cell, or in the special organization 
of the potentiality, for one of these of its own initiative being developed 
earlier or later ; nevertheless, according to the species, the special 
conditions which dominate the kinds of propagation may be more or 
less readily realized in open nature, as well as in the laboratory. 
In particular, the sexual propagation is often dependent upon more 
complex conditions than the non-sexual. While both can be induced 
without difficulty in Sporodinia , in other J^fucorini it is most difficult 
to see the zygospores at all. I have not succeeded in my attempts 
to induce the formation of zygospores in the common and easily 
cultivated Mucor racemosus , though such formation doubtless exists. 
In the works of Brefeld the idea is often expressed and tested 
of bringing a Fungus by culture through the most numerous successive 
conidium-forming generations to its higher fruit-form. This idea is 
connected with Brefeld's idea that inner causes are more important 
than external causes for the appearance of the fruit-form. The result 
of the serial cultures of Brefeld, whether positive or negative, was 
under all circumstances accidental. The experiments would prove 
the view of Brefeld only if the external conditions had really been 
always the same in all the numerous serial cultures. Since Brefeld, 
to judge from the meagre statements of his methods of culture, has 
not paid any attention to this constancy of the conditions, it will also 
have been a matter of chance whether they remained the same, or 
varied in such a way that another form of fruit took the place of that 
which preceded it. In any case, I may assert that if in Fungi such 
as Sporodinia , Saprolegnia , Ascoidea, Eurotium , those external con- 
ditions are maintained constantly which are characteristic for one of 
the forms of propagation, that same form only is produced. Hitherto 
