416 Prof, H. Karsten on the Formation, 
take place much more rapidly in the colourless endogenous cells, 
especially with the latter solution, whilst their contents remain 
uncoloured and readily mingle with the fluid. 
Sometimes, immediately on cutting through a Conferva in 
water, a large thin-walled cell, of half the length of the joint-cell 
and equal to it in diameter, may be seen to emerge gradually : 
it is filled with other vesicles, partly clear and transparent, and 
partly coloured green and containing chlorophyll- and starch- 
corpuscles. It looks, in fact, as if an entire young joint-cell 
were thrust out from the cell of the Conferva. After a short 
time, the outer wall (the mother cell of all these enclosed cells) — 
dissolves in the water, and either suddenly vanishes in its whole 
circumference or its solution proceeds from one extremity and 
advances throughout its entire extent, when all the enclosed 
corpuscles, previously recognizable only by the flattening of their 
contiguous walls, project more or less above the surface of the 
conglomeration, and, expanding continually, at last burst and 
suddenly disappear. 
The phenomena are different when the section of the Alga is 
effected in a solution of gum arabic instead of under water. 
Then, as the fluid penetrates into the cut Algal cell, no green 
cells, and scarcely any but perfectly limpid cells, make their ap- 
pearance ; and these present a more deceptive resemblance to 
drops than even in water. They may be seen to exude in suc- 
cession from the interior of the Conferva joint-cell in great 
abundance and of very various dimensions, and, as they approach 
the aperture, to increase in size, and soon-entirely stop it up. 
Sometimes they are coated with a green slime; sometimes this 
is collected into a larger mass, which is surrounded by the trans- 
parent cells, and in which they are imbedded. 
On gradually adding water to the solution of gum, these 
hyaline cells, usually called vacuoles, are seen to swell up gradu- 
ally until they collapse suddenly, when their contents mix with 
the water, and their membrane shrivels up, but for the most 
part is not dissolved. The green mucilaginous masses likewise 
now begin to swell, and it can be distinctly perceived that these 
are the vesicles filled with green mucus which collapsed in the 
solution of gum, whilst their membranes enveloping the green 
slime are now again distended in the water. 
The membranes of the cells filled with a colourless strongly 
endosmotic fluid, which have burst in the water, may be treated 
with corrosive reagents without being immediately dissolved. 
_ On submitting them to an aqueous or alcoholic solution of 
iodine, it is found that that reagent does not perceptibly colour 
either the contents or the membrane of these cells. The same 
holds true, in the main, when the solution of chloride of zine 
