Mr. H. J. Carter on Eudorina elegans. 11 



when every part is reduced to singleness within one little sphere, 

 and the whole of this little sphere is watched during its (Econo- 

 mical operations, the value of the different organs which it con- 

 tains becomes most obvious. Thus, this little cell, which is so 

 numerous in the cells of the larger Alga?, seemed of so little im- 

 port compared with the "nucleus" of the cell, that when I came 

 to observe the most conspicuous cell or organ in the single Algal 

 cell undergoing division provisionally for a subsequent duplica- 

 tion of this cell, I could not help at first viewing it as the 

 " nucleus ;" but subsequently observing that this organ was in 

 the midst of chlorophyll, which, again, was most densely accu- 

 mulated round its margin, its frequent and variable plurality, 

 and, above all, its becoming purple by the addition of iodine, 

 its identity with the starch-cell in the reticulate chlorophyll of 

 QLdogonium, in the green bands of SjArogyra, and in the green 

 layers of Nitella, &c., became complete. 



To the term " cell," or " utricle" as it is called by Nageli, how- 

 ever, Mohl objects,observing that it is only a part of the protoplasm 

 (coloured with chlorophyll) defined by a circular line which "is 

 firmer than the internal portion," and that it cannot be demon- 

 strated to have a cell-wall any more than " a cheese," — that " this 

 is not enough to constitute a membrane, for it is indispensable 

 to the notion of the latter that it forms a layer definitely bounded 

 on both sides," — and that " it is by no means to be denied that 

 a globular mass of organic substance may acquire a membranous 

 coat, through a hardening of its outer layers, and become con- 

 verted into a utricle in the manner stated by Nageli. But for 

 the application of this expression to be fitting and admissible, it 

 is quite requisite that the said process should actually have taken 

 place, that a separation of envelope and contents should have 

 occurred*." To dispute such high authority would, in one who 

 has not given his attention particularly to the subject, be not 

 only unwise but wrong, and to attempt to demonstrate a mem- 

 brane round the "nucleus" or "starch-cell," while either is 

 fresh and plastic, and in active vital operation, I think, with 

 Mohl, almost impossible ; but when, from age, disease, or acci- 

 dent, the contents of the Algal cell become more or less de- 

 vitalized, then, I think, both the nucleus f and starch-cell will 

 be found to be circumscribed by a membranous covering. With 

 the "nucleus" I have nothing to do here, and shall only obsex-ve, 

 respecting the starch-cell, that in the green layer of Nitella, as 

 I have already figured and stated J, the chlorophyll-disks may 



* Mohl, On the Structure of Chlorophyll, translated by Prof. Henfrey, 

 Annals, vol. xv. p. '622, 1855. 



t Annals, vol. xix. p. 25, pi. 3. fig. 11, 1857. 

 X Annals, vol. xvii. p. 104, pL 8. figs. 3-5, 1856. 



