120 Mr. H.J. Carter on the Circulation of the 



includes the rotatory movement seen in the cells of many aquatic 

 plants besides the Characeae^ in which the whole of the mucus- 

 layer changes place. In Serpicula verticillata (Roxb.), the green 

 disks are imbedded in the mucus-layer promiscuously, and are 

 carried round the cell with it ; and in Tradescantia the cytoblast 

 also goes round with the mucus-layer. To this perhaps might 

 be added the polymorphism of the granular mucus occasionally 

 witnessed on the septa between the cells of Spirogyra (p. 19), 

 unless this also be owing to the presence of a rhizopodous 

 organism. 



There is yet however another kind of motion, which has been 

 observed in Closterium Lunula, and some other Desmidise ; and 

 this, according to the Rev. S. G. Osborne's observations, con- 

 firmed by Mr. Jabez Hogg*, is owing to cilia situated on the 

 surface of the mucus-layer. By their action, which appears to 

 be very irregular, and is certainly very perplexing, the brown 

 corpuscles are urged backwards and forwards, or circulated 

 more or less round the frond. The same kind of motion is 

 witnessed in similar corpuscles in Spirogyra, which, coming 

 next to Closterium in point of organization, may be found to be 

 provided with similar organs. There is no analogy, however, 

 between the circulation of these corpuscles and the rotatory 

 movement of the mucus-layer of Nitella, nor between it and the 

 circulation of the axial fluid of the latter and its particles. To 

 assume that the mucus-layer of the internode of Nitella is urged 

 on by cilia, would be to assume that the cilia are not on the 

 surface of the mucus-layer, as in Closterium, but on the inner 

 surface of the green layer ; and then, in the roots, that they are 

 on the inner surface of the cell-wall, for there is no green layer 

 there, — which would be absurd. Again, we can see that the 

 particles contained in the axial fluid are impelled by the irre- 

 gular surface of the mucus-layer, and this seems quite enough 

 to account for this circulation. 



As regards the general irritability of the mucus-layer, this by 

 itself is of course no proof of locomotive power, but occurring 

 in homologous structures, it allies them in point of property as 

 well as structure, and therefore aff'ords additional reason for 

 admitting the phsenomena observed in one as confirmative or 

 explanatory of those which are observed in another organism of 

 the same or similar nature. Hence, if we have evidence of a 

 locomotive power in the mucus-layer of the cells of Spirogyra, 

 and the object to be gained by it, as well as evidence of the same 

 power in the mucus-layer of the internode of Nitella, though 

 the object be not manifest, our conclusion, that the latter is 



* Quart. Joui'n. Microscop. Soc. vol. xi. p. 234, 1854. 



