442 Mr. A. Henfrey on the Prog'ress of Physiological Botany. 
scribes sucb a structure under the name of i\iQ primordial-schlauch, 
which I have translated and adopted in my*own researches under 
the name oi primordial utricle. Unger* also takes the same view. 
Nageli maintains that there is no special membrane inclosing the 
cell-eontents^ and like Prof. Mitscherlieh he believes that the ap- 
pearances which the protoplasm presents when coagulated on the 
surface have deceived the above observers. My own observations f 
have led me to agree with H. von Mohl, and the independent 
membranous nature of the primordial utricle is also asserted by 
K. MullerJ. 
The action of the protoplasm in the production of the septum 
in cell-division is therefore either immediate, as asserted by 
Nageli §, who declares that it secretes the new membrane or 
thickening layers, as the case may be, or it is the investing mem- 
brane of the protoplasm, the primordial utricle, on the surface 
of which the new deposits are formed and moulded. 
Nageli says, that the protoplasm divides into two complete 
portions, at once, and deposits the septum, perfect, though as yet 
very thin. Unger also describes the division of the primordial 
utricle as being effected at once, and the formation of the whole 
septum as simultaneous. 
It has just been seen that Prof. Mitscherlieh holds the forma- 
tion of the septum to be progressive ||, and H. von Mohl^ de- 
scribes and figures the whole series of stages which he saw, and 
which convinced him that the process of formation proceeds from 
the periphery to the centre ; that the primordial utricle gradually 
folds in, and secretes the cell-membrane as it advances. My own 
observations** agree with this view, and it is principally supported 
by what I saw in common with H. von Mohl, namely the con- 
tinuation of the cell- contents through the imperfect septum. 
However Nageli states that this appearance is produced by the 
adherence of the contents to the centre of the septum. On the 
other hand, I believe with Von Mohl that the conclusion that the 
contents are divided into two parts at once may be founded on an 
error caused by the action of reagents, which when they cause the 
protoplasm and primordial utricle to contract violently, also fre- 
quently produce a rupture across the isthmus which connects tlie 
contents of the two parts of the dividing cell. 
* L. c. supra. 
t Ann. of Nat. Hist. Ser. 1. vol. xviii. p. 364, 1846. 
X Zur Entwickelungsgeschichte cler Charen. Botanische Zeitung, vol. iii. 
1845, — Translated in the Ann. of Nat. Hist. Ser. 1. vol. xvii. 1846. 
§ Zellenkerne, Zellenbildnng, &c. Zeitschrift fiir Wiss. Bot., Heft 1 & 3. 
The former paper is translated in the Ray Society’s publications, 1845. 
II Prof. Mitscherlieh does not attribute any function to the cell-contents. 
^ Vennisch. Schrift. p. 363, 1845. 
** Ann. of Nat. Hist. t.c. 
