144 DIVISION II.—COURSE OF DEVELOPMENT OF FUNGI. 
of species which agree with Achlya in other respects have the last named peculiarity 
alone, and their spores do not collect into heads; these are included under the generic 
name of Dietyuchus. Some histological details will be found in section XVIII. 
The formation of swarm-spores in the germination of the oospores agrees in every 
known instance with the character assigned to the genera, but has not yet been observed 
in Dictyuchus. 
Aplanes, a new genus, identical probably with Reinsch’s Achlya Braunii, very 
rarely forms gonidia on the developed thallus, but more often in the germination of 
the oospores. The gonidia are formed as in other genera; in the germination of the 
oospores either directly in the cavity of the oospores, or in a single row in sporangia 
on short-lived dwarf plants. They put out short germ-tubes at once in the place 
where they are formed, nor have I ever been able to perceive any appearance of 
swarming. 
Resting gonidia. In old tufts, those of Saprolegnia especially, it not unfrequently 
happens that the thick thallus-tubes become broken up by transverse walls into cylin- 
drical, barrel-shaped, or inflated spherical cells, which are sometimes thick-walled and 
always rich in protoplasm. In some species, and especially according to my own 
observation in Achlya prolifera, these cells may be very large and spherical, unusually 
full of protoplasm, and abjointed serially and successively at the end of a tube 1; 
All such cells may under favourable circumstances—in pure water containing free 
oxygen, and when supplied with suitable food—either develope directly into new 
thallus-tubes or become swarm-sporangia (the resting sporangia of Pringsheim). 
They are not, as far as we know, characteristic of particular species, but simply 
resting states which frequently make their appearance under the influence of external 
causes. 
The deviation in the structure of some oospores from the ordinary type has 
been described by me at length in another work? It occurs in a few species of 
Achlya (A. polyandra and A. prolifera), in Dictyuchus clavatus and in an undescribed 
Saprolegnia, and is not generally characteristic of any of the genera in question. 
Leptomitus lacteus and L. brachynema are imperfectly known forms, belonging 
probably to the Saprolegnieae, with their thallus-tubes constricted at intervals and 
with swarm-spores formed in a similar manner to those of Saprolegnia; with respect 
to Cornu’s genus Rhipidium the author’s short preliminary description leaves it 
uncertain whether its place is here or with the Peronosporeae near Pythium. 
Controverted points. Pringsheim has recently put forth some views which if 
correct would require a modification to some extent of the account here given of the 
Saprolegnieae, but only so far as concerns the possibility of a fertilisation of the 
oospheres by the antheridia, 
Pringsheim claims the office of fertilisation for some small portions of protoplasm 
with amoeboid movements, which are supposed to make their way through the closed 
‘wall of the fertilisation-tube and to pass into the oosphere. Pringsheim has never 
seen this take place ; he only suspects it on the evidence of some stained preparations, 
which seemed to show a possible open communication between the protoplasm of 
the oosphere and that of the antheridium, and of a peculiar phenomenon observed 
in the antheridia of Achlya racemosa, the account of which must be read in the ori- 
ginal publication, but which has certainly nothing to do with the process of fertilisation. 
His observations moreover refer to other species than those specially described above. 
If there is really an open communication in those species between the protoplasm of the 
antheridiam and oosphere, which, as has been said, is extremely doubtful, we must 
admit a fertilisation in their case, and in the mode already described in Pythium 

1 Walz in Bot. Ztg. 1870, t. IX, Fig. 20. ? Beitr. IV, p. 69. 
