Naoiculaeea.] infusorial animalcules. 303 



Ai'c the Diatomacea plants or animals? is still a questio vexata. 

 The able discussion of this point by Meyen, in the case of the 

 Bac'dlaria, generally, is given in the previous pages ; and here ia 

 appended a summary, by Kiitzing, of th.e arguments urged on each 

 side in the case of the Diatomem. 



" For their animal nature, Elircnberg presents the following 

 arguments. 



1. The Diatomca exhibit, in part, a peculiar spontaneous move- 

 ment, wliich is produced by certain locomotive organs. 



2. The greater part have in the middle of the lateral surface an 

 opening, about which round corpuscles are situate, which become 

 coloui'ed blue when placed in water containing indigo, like as do the 

 stomach-cells of many Infusoria, and, consequently, they may also be 

 regarded as stomachs. 



3. The shells of many Diatomacecs resemble, in structure and con- 

 formation, the calcareous shells of Gasteropoda, and similar Mollusca. 



Of ihe first argument, it may be observed, that spontaneous motion 

 is met with also in the lower plants, in which, moreover, it arises from 

 special ciliary locomotive appendages. I would instance the obser- 

 vations of TJnger on Vaucheria cla/vata of Flotow on Hernato- 



coccus pluvialis, and lastly my own (in the Phycologia c]eyieralis) on 

 Ulothrix zonata, and other Algae ; all which shew that in these lower 

 organisms evident movements occur, not to be distinguished from those 

 of the Infusoria. 



Hence this argimient fails. 



As to the second position ; the colouring of the so-called stomach- 

 cells by indigo, as I have before proved, is probably but a mechanical 

 operation ; and affords no evidence of their stomach-like character, 

 and especially as the vesicles are often wanting. 



Of the third argument. The shell has frequently, indeed, in 

 stnicture, conformation, and markings, a similarity to that of 

 MoUusca, but this is not invariably the case, and we find among the 

 cells of higher plants, those which, in configuration, form, and other 

 particulars, exhibit similar aj)pcarances. For instance, the numerous 

 forms of pollen, with their angles, spines, orifices, &c. In this matter, 

 relation of form, therefore, the DiatomecB stand as closely to vegetable 

 as to animal structures. 



