442 Mr. A. Henfrey on the Progress of Physiological Botany. 



scribes such a structure under the name of the 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-contents, and like Prof. Mitscherlich 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. Miillert. 



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. Mitscherlich 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 IMohl 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 the 

 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 der Charen. Botanische Zeitung, vol. iii. 

 1845.— Translated in the Ann. of Nat. Hist. Ser. 1. vol. xvii. 1846. 



§ Zellenkerne, Zellenbildung, &c. Zeitschrift fiir Wiss. Bot., Heft 1 & 3. 

 The former paper is translated in the Kay Society's publications, 1845. 



II Prof. Mitscherlich does not attribute any function to the cell-contents. 



Tf Vermisch. Schrift. p. 363, 1845. 



** Ann. of Nat. Hist. I. c. 



