LIFE OF THE PLANT-CELL. 101 



In Achlya pronyera, no observation has yet been published serving to 

 throw light upon the mechanism of this motion ; my own observations 

 date at a period in which I first began the pursuit of Botany. In Vau- 

 cheria clavata I have only once observed a liberated and spontaneously 

 moving spore, and immediately noticed currents on each side of it, rendered 

 manifest by the rapid transit of minute corpuscles. I thereupon concluded 

 that these currents were produced by cilia, but in trying to fix the spore 

 and observe it more closely it was unfortunately destroyed. linger, and, 

 after him, Thuret, have communicated more particular observations on 

 this subject, and shown that the whole exterior of the cell is covered with 

 vibratile cilia. Thuret has also observed motion and vibratile cilia as the 

 cause of it in Conferva rivularis and C. glomerata, in two species of Ch<z- 

 tophora, and two of Prolifera. (?) Kiitzing simply noticed the motion in 

 Achlya prolifera, Tetraspora gelatinosa, and Ulothrix zonata, without 

 making any observation on its cause. Excepting in those of Achlya 

 prolifera, Vaucheria clavata, and Tetraspora gelatinosa, Kiitzing and 

 Thuret found in the self-moving spores a reddish spot, like that in the 

 green monads, and termed by Ehrenberg " eye-points." Kiitzing observed 

 this spot in the spores, not only whilst yet in the sporangium, but also 

 even in the first or second cell of the spore when becoming developed into 

 a Conferva. All these spores, except those of Achlya prolifera, are 

 green ; whilst Kiitzing states it as a law, that in all the lower Algce 

 (his Isocarpece) the true and mature spores are brown. More pre- 

 cise and comprehensive observations on this phenomenon are still indis- 

 pensable before any conclusive result can be drawn from them. Are there 

 not probably spores whose completion is not yet effected, in which the 

 formation of the cell-membrane from the tender mucus-layer has not been 

 as yet perfected, which lose their cilia (mucus ?) and become capable of 

 development as soon as the formation of the cell-membrane is quite 

 completed ? 



The lower Conferva, filamentous Fungi, &c., have at all times af- 

 forded the most fertile field for the mystical dreams of fancy, because in 

 no part of Botany are researches so difficult to make, and so much out of 

 our power to control. Here, more than any where else, it is necessary, in 

 order to escape all unscientific, fanciful delusions, to be guided by the 

 maxims of a sound philosophy. Particularly is it necessary in this case, 

 if we do not wish to deprive scientific research of all certainty, at once to 

 dismiss from consideration every observation that has not been made 

 upon indubitable plants. I have consequently, in considering this question, 

 as elsewhere, left entirely out of the field the Diatomacecs, Bacillarice, &c. ; 

 in short, all those forms the animal nature of which has been asserted by 

 Ehrenberg, upon grounds at all events worthy of consideration. Whoever 

 is interested in this subject, will find in the masterly works of Ehrenberg, 

 especially in his great one on the Infusoria, as well as in the diligent 

 labours of Kiitzing, a great mass of historical matter, collected with the 

 most extraordinary industry, together with abundance of remarkable 

 original observations. As a basis, however, for the foundation of botanical 

 laws, these materials should not be employed. 



Only a science crazy with fantastical mysticism, and far removed from 

 a clear, self-intelligible Natural Philosophy, could entertain the dreamy 

 notion that creatures may be at one time animals and at another plants. 

 Were this possible, it would necessarily much more readily happen that 

 a being should be now a fish and now a bird ; or at one time a conferva, 

 at another a rose ; and then what would all our natural science be but 



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