284. Prof. H. Karsten on the Formation, 
itory seeretion-cells or the early stages of development of new 
joint-cells. 
It has been satisfactorily shown by former observers, and 
especially by Bary, that the thickened membranes of Gidogonium, 
and particularly the extensile annular fold, behave with reagents 
like cellulose. To these statements I can add that this annular 
fold consists solely of cellulose, even before its extrusion. 
In the ordinary course of development of Gidogonium, this 
investigation is difficult, on account of the instantaneous rupture 
of the membranous envelope, and the sudden extension of the 
fully developed fold, on the application of the reagents necessary 
for these experiments. 
In specimens placed in the direct rays of the sun, in order to 
excite them to more rapid development, but which had to sup- 
port a temperature too high for their normal vegetative activity 
(namely, 35° Réaumur), the membranes of the secondary cells 
acquired considerable thickness whilst yet enclosed within the 
paary cells, which stall exhibit their annular folds, as shown in 
ow, 25. 
In these cells it could be seen distinctly that the annular 
constriction consists entirely of cellulose—that is to say, that it 
exhibits the cellulose reaction with solution of iodine and chloride 
of zinc—as the annular fold did not extend itself even on the 
application of that reagent. 
The contents of these unusually thickened cells consisted of 
comparatively large hyaline non-nucleated cells, with pale-green 
starch- and chlorophyll-corpuscles and reddish-coloured oil- 
drops (?) thinly scattered between them. <A large accumulation 
of chlorophyll was observed in the upper end of the cell. 
These Gidogonia soon became quite colourless; the large 
transparent vesicles disappeared ; and only the oil-particles, and 
especially the decolorized starch-corpuscles, remained undis- 
solved and unchanged in the dead membranes for any con- 
siderable time; even the annular fold vanished by solution, 
though the rest of the same cell-wall continued unaltered. 
Similar individuals, with greatly thickened secondary cells, I 
have observed now and then among normally developed forms. 
In these also the annular fold had not expanded, though the 
imvesting envelope, consisting of a double membrane (probably 
the cuticle and the remainder of the membrane of a primitive 
mother cell), was annularly torn through above it. Indeed, in 
a few days, the fold was dissolved in the water, and its former 
existence evidenced only by an empty space. In these cells two 
young joint-cells had been formed—one, the larger, occupying 
the space below the annular fold, the other the small space of 
the mother cell above that fold, Both these young cells were 
