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 arable 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 thp solution of chloride of zinc 



