on the Saprolegnieae . 209 
contraction is the complete rapture of the continuous pro- 
toplasmic investment of the walls into segments belonging 
to each origin. This is easily seen in poor sporangia — in 
optical section the protoplasmic investment can be seen to 
rise and divide between two origins, and go half to each. At 
this moment the origins (now spores) become full of minute 
vacuoles, which diminish in number and enlarge as the spores 
swell and the protoplasm becomes finely granular. ‘ It is here 
quite clear that the two processes, the vacuolation and the 
swelling up of the spores, go hand in hand ; the phenomenon 
of swelling is easy to understand if we make the really obvious 
supposition that the protoplasm of the spores has a tendency 
to take up water. This could not hitherto have full play so 
long as the “ Hautschicht,” which must be regarded as con- 
tinuous, hindered endosmose : but when the investment of the 
wall is ruptured, the “ Hautschicht 55 is interrupted at the points 
of severance, and before its reconstitution cell-sap is taken up 
into the protoplasm of the spores and determines their swell- 
ing. The cell-sap so absorbed, or. a part of it, is at once 
excreted in the form of the shifting vacuoles V I must here 
note that in my paper in 1886 I had pointed out that 
‘probably the “Hautschicht” and vacuolar wall break up at this 
stage and become reconstituted later on, and that herein is 
the true essence of the homogeneous stage,’ which I had 
written a page above 4 consists essentially in the swelling up 
of the protoplasm, and the loss of its resistance to osmosis.’ 
I thus had perceived and demonstrated the essence of the 
homogeneity; but owing to the unfavourable type I had chiefly 
worked over I had failed to discover the rupture of the 
continuous ‘ Wandbeleg, 5 which is undoubtedly its proximate 
cause. The demonstration of this belongs to Rothert and 
Rerthold. I also demonstrated to Prof. De Bary and Dr. 
Biisgen in 1884 the loss of turgescence of the sporange, 
and its marked contraction, accompanied by the bacterial 
dance. 
1 In fact the vacuolation is really paralleled by such cases as the vacuolation 
of the protoplasm of a tom Vaucheria filament. 
