MICROSCOPIC ALG^ AND FUNGI. 211 



motile cilia is the same in each group ; for whilst all green 

 swarm-spores have at least two cilia, the colourless monads 

 and the swarm-cells of Chytriclium certainly have but one;* 

 in Aclih/a also, Pringsheim observed but one, which accords 

 with Cohn^s own observation, though Thuret and De Bary 

 assert positively that they have seen two. 



To this it may be added, that a great part of the Infusoria, 

 and in fact not merely of the lowest, but also of those standing 

 comparatively high in the scale, enter into a quiescent state, 

 in which they lose all perceptible vestige of movement and 

 organization, and become invested with a rigid, perfectly- 

 closed membrane ; apparently in precisely the same way that 

 vegetable swarm-cells, when germinating, secrete a tough 

 cellulose-membrane. And in particular, do the true monads 

 present a condition of encysting, in which they cannot be dis- 

 tinguished from colourless, c|uiescent (fimgus-) cells. Conse- 

 quently, since neither the 'swarm-cells' of the aquatic fun yi 

 exhibit any tenable criterion by which they can be distin- 

 guished from monads, nor the encysted monads any by which 

 they can be distinguished from the germinating aquatic y)/??^//, 

 there is no wonder that, in many cases, it is almost impossible 

 to determine to which category a given organism may belong. 



Cohn, however, seems still indisposed to regard all the 

 Ehrenbergian monads as developmental states oi fungi, as he 

 has convinced himself, he says, of the correctness of Ehren- 

 berg's observation, that many, even very minute species, when 

 kept for some time in coloured water, take up particles of 

 indigo. This circumstance, Cohn regards as sufficient proof 

 of the existence of a mouth, and consequently, of the animal 

 nature of the organism ; in neither of which points, however, 

 do we coincide with him. 



3. The family of the Volvocina affords so many points 

 of interest and importance, that the study of it may, to a cer- 

 tain extent, be regarded as a fundamental basis for the know- 

 ledge of microscopic organisms in general. 



The vegetable nature of these organisms, first distinctly 

 recognised by Siebold, and at present admitted by nearly all 

 observers, has already been copiously discussed in the pages 

 of this Journal, and the subject need not here be further 

 adverted to. 



The Volvocina, in general, may be said to consist of two 

 parts, a colourless hyaline investing cell (Hiillzelle), consist- 

 ing of cellulose [?], and of green jmmordial cells.j The 



* In Euf/lena, however, which is deeply coloured, there is but one 

 ciliuTn. 



f For the explanation of these terms, vide Cohn, rrotococcns pluvialis 

 (' Botanical and Physiological Memoirs,' published bv the Eay Society, 

 1853). 



p 2 



