M. H. V. Mohl on the Structure of Chlorophyll. 325 



anatomical conditions, such diverse conditions must not be con- 

 founded together*. No less totally unfit is it, if we would ad- 

 here to the universally established notion of the utricle, to apply 

 the name utricle to a more or less soft, yet not fluid, globular 

 mass, the surface of which is of firmer consistence, for the 

 notion of a utricle is essentially that of a cavity surrounded by a 

 solid substance either filled with a liquid or gaseous fluid or 

 quite empty. But it is common to all the structures described 

 by Xageli as utricles, that they have neither an envelope distin- 

 guishable from the contents, nor a cavity, while the vacuoles, 

 which he does not call utricles, actually possess both. Thus, no 

 expression can be more misapplied, for the denomination of the 

 former structures, than that of a utricle. With as much right 

 could we give the name bladder to a cheese which has a rind 

 resulting from the drying of its surface, for in its essential rela- 

 tions it does not much disagree, although on a larger scale, with 

 Nageli's latricles consisting of proteine-substance. 



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 converted into a utricle, in the 

 manner stated by Nageli. But for the application of this expres- 

 sion to be fitting and admissible, it is i-equisite that the said pro- 

 cess should actually have taken place, that a separation of enve- 

 lope and contents should have occurred. In his recent treatise 

 Nageli leaves it wholly in obscurity, whether he now, as for- 

 merly, regards the granular structures of the vegetable cell as 

 surrounded by a coat with a double outline, or not, — pro- 

 bably the former, since he does not acknowledge as erroneous 

 the circumstance, that a membrane exists, but only the point, 

 that he had incorrectly believed this to consist of cellulose, and 

 objects it to me, as something inconceivable, that I have not yet 

 detected this membrane. This however will at all events never 

 make any one believe, who has seen a chlorophyll-granule or 

 a starch-granule through a good microscope, that the figures 

 in plate 3 of his ' Zeitschrift ' are correct, in which he (especially 

 in figs. 10, 12, 14, 15 & 17; Ray Society's volume for 1849, 

 pi. II. figs. 10, 12, &c.) represents these granules clothed with a 



* It is an evident imperfection of our anatomical terminologv', that we 

 possess no expression to indicate such a condensed surface in contra- 

 distinction to a real membrane. The naturalists who describe the Infusoria 

 have the same difficulty ; thus Dujardin, for example, says, on a similar 

 occasion, " I willingly admit that this surface may, by contact with the 

 surrounding liquid, acquire a certain degree of consistence, like tlour-paste 

 or clue allowed to cool in the air, but simply in this manner, and without 

 the production of a layer differently organized from the interior." I pro- 

 pose to apply to such a consolidated surface the term pellicula. 



