from the Cell-contents of the Characese. 105 



Mucus-layer. — It has been already stated that when this 

 rushes out it is found to be composed of a granuliferous mucus, 

 globular vesicles, circular disks, and irregularly shaped opake, 

 yellowish bodies. The disks, which are circular in the small 

 Nitella, are elliptical and elongate in the large one; and the 

 irregularly shaped bodies, which have no particular figure in the 

 small 'Nitella, are, for the most part, agariciform and patulous in 

 the larger species. The same differences obtain also in Chara 

 verticillata (PL VIII. figs. 7-16). 



Although many of the globular vesicles present no nucleus, 

 and many appear to be altogether void of granular contents, 

 yet most present either a single nucleus or a plurality of such 

 nuclei ; and some which are very large contain a number of 

 smaller nucleated vesicles like themselves ; but the typical form 

 of the globular vesicle consists of a transparent cell-wall filled 

 with a granuliferous mucus, the grosser parts of which are more 

 or less collected round the nucleus, which is fixed to or imbedded 

 in its cell-wall (fig. 14) ; the nucleus being, in fact, equivalent 

 to the " circular disk " (fig. 8) ; and where we see a plurality of 

 them in a globular vesicle (fig. 16), it may be inferred that they 

 are developed there, and that the subsequent bursting of the 

 vesicle thus allows them to become free and scattered in such 

 abundance as they are observed to be throughout the mucus-layer. 

 Another remarkable character of this delicate vesicle is, that it 

 is endowed with the power of motion, inasmuch as many may be 

 seen on their first issuing to rotate upon their axes, and to un- 

 dulate or prolong their cell-wall in different directions, while the 

 granules of the mucus internally are in constant vibratory or 

 molecular movement, like those of Spirogyra (produced perhaps 

 by the irritability of the mucus) ; while the mucus itself en 

 masse is continually moving to this side or that, and drawing 

 all the granules which are imbedded in the moving portion in 

 the same direction. Hence, with the exception of the contract- 

 ing vesicle and a far more delicate texture, we have a cell corre- 

 sponding in every respect to that of Amoeba and Spongilla. 



It will be remembered also, that in my description o/ Spon- 

 gilla * it is stated, that the intercellular mucus which binds the 

 cells together has a polymorphic power, like that of the cells 

 themselves ; and this appears to be the case, but in a much more 

 limited degree, with the granuliferous mucus of Nitella, which, 

 at the time of its issuing from the internode, in masses, under- 

 goes a slow but appreciable change of form ; and either throws 

 out threads which adhere to the glass, or exhibits in these 

 threads a distinct retractile movement when the latter separate 



* Ann. and Mag. Nat. Hist. vol. iv. p. 36, 1849. 



