IV. On the conlinuity of thc protoplasm through (he walls of vegetable cells. 79 
U now remains for me to put forward some explanation of the pheno- 
mena of Plasmolysis. There are two questions to be answered. The first is, 
wTiy is it that the main protoplasmic mass when contracted from the cell- 
wall remains connected with it on all sides by delicate protoplasmic Strands? 
The second is, what is the explanation of the fact that these Strands are at 
first invisible, and then gradually come into view ? It will be observed that 
I am dealing here only with the Plasmolysis caused by dilute Solutions of a 
neutral salt. 
To explain the first question Bower suggests two views — "1) that the 
main mass of protoplasm on retreating may leave the cell-wall still com- 
pletely lined with a thin layer of protoplasm; 2) that the peripheral part of 
the protoplasm being cntangled as a network among the deposited microso- 
raata, may on contraction of the main mass be drawn out at the points of 
entanglement into fine Strands like those observed, while the surface of the 
W all is for the most pari left free and not covered by a film of protoplasm.” 
Unfortunately ncither of these views admit of being practically tested. 
Although a careful examination of most delicate sections of material which 
has been plasmolysed, fixed with Picric acid, and stained with Hoffmann’s 
blue does not demonstrate the existence of such a thin layer, but only shows 
the little spherieal masses which are either connected with a Strand going 
to the main mass, or are formed in eonsequence of the rupture of Strands, 
and demonstrates moreover that these masses are sharply defined from the 
cell-wall, yet it is perfectly possible that such a delicate layer might be 
present and yet be invisible. Again if the cell-w r all be actually formed by 
the Opposition and coalescence of microsomata as described by Strasburger, 
it is not impossible as Bower points out that some portion of the peripheral 
protoplasm may be entangled as a network among the deposited microso¬ 
mata. But whelher this be so or not I am of opinion that a still simpler 
explanation may be giveu. To borrow a simile from physics, the cell-wall 
is so perfectly wetted, so to speak by the protoplasm, and at the samc time 
this latter body is so extremely piastic, that it appears not improbable that 
when Plasmolysis is induced, the protoplasm while separating at certain 
points, from the cell-wall, adheres strongly to it at olhers, and is thus 
drawn out into a number of delicate Strands, in the same way as a piece of 
stringy mucus adhering to the side of a glass tumbler may be draw n out 
into Strands of great tcnuity. That particular combination of forces which 
exists at the time, determines which part shall adhere and which shall 
come away. 
As to the second question Bower again puts forward two explanations. 
The increase in thickness of the Strands may be produeed "1) by the draw- 
ing out of a fresh supply of subslance from the main protoplasmic body or 
2) by the lateral coalescence of originallv separate Strands." I am disposed 
to think that in certain instances the latter phenomenon may occur, but it 
