213 
on the Sctprolegnieae. 
processes as the sporangia : formation of oosphere { anlagen ’ ; 
development of septum ; rupture of the connecting layer ; 
swelling of the oospheres ; excretion of cell-sap, as shown by 
a contraction of the oogonium and the assemblage of swarming 
Bacteria. After this swelling the oospheres (oospores Rothert 
terms them) contract and round off, excreting lumps of pro- 
toplasm and taking them up again. They also show the same 
dark granules on treatment with iodine. In position as in 
development zoosporangia and oogonia are homologous; which 
is to be developed seems rather a matter of date than anything 
else : a hypha cut off to-day produces the former ; to-morrow 
or the next day it would have produced the latter ; but on the 
whole it appears that cultures from successive generations of 
zoospores tend to produce oospores more readily, and recent 
cultures from oospores produce especially abundant crops of 
zoosporangia. To this I may add that cold, and drying up of 
the water (to a less degree), both tend to induce the early for- 
mation of the sexual fruit. 
I have found in a Saprolegnia , which I believe to be De 
Bary’s S.ferax , form toraloso , that small cultures drying up 
tended to produce spheroidal dilatations at the ends of fine 
hyphae which were cut off by septa. On moistening, the con- 
tents became ordinary zoospores, and these were freed by 
deliquescence of the cell-wall. 
In his supplement or 4 Nachtrag,’ Rothert first gives an 
abstract of Berthold’s confirmatory work : and then proceeds 
to investigate my theory of liberation, which I ascribe in my 
paper ‘ not to any such expulsive matter as has been assumed, 
but to the chemical stimulus of the oxygen in the medium 
acting on the automotile zoospores.’ He asserts that I have 
founded this on insufficient data, and have pushed it too far, 
as it cannot apply to Aphanomyces , Achlya (other than those 
species which Cornu and I have examined), and to Dictyuchus , 
for that these have no cilia. I have already shown that the 
probability is that flagella will everywhere be found when 
properly looked for in the escaping zoospores of Achlya and 
Aphanomyces. The genus Dictyuchus , in which the spores 
