150 GENERAL HISTORY OF THE INFrSORIA. 



actively in the water. During their motion they excrete a delicate cellular 

 membrane o\X'r their entire surface, which is gradually removed farther and 

 farther from the primordial utricle by endosmose of water, imtil at length it 

 becomes the vnde envelope of the mo^dng form described above. From this 

 it follows that the latter forms do indeed possess on the whole the character 

 of simple cells, but display some peculiarities in theii' stractm^e and develop- 

 ment, since the internal coloured globule corresponds originally to the pri- 

 mordial utricle of other vegetable cells, yet is not surroimded by a membrane, 

 as usual, but suspended free in it like a ceU-nucleus, while watery, unazotized 

 contents appear between the membrane and the primordial utricle. For this 

 reason I have called the enclosed coloured globule, which is formed first, and 

 originally moves about without a special membrane in the manner of a cell, 

 and corresponds to the primordial utricle of vegetable cells in general, the 

 j^rimordial cell, and the enclosing membrane "^ith its watery contents the 

 envelope-cell. The moving Chlamiidococcus-QOTidiitioii is capable of propagating 

 as such, by the enclosed primordial cell dividing anew, the individual portions 

 slipping out of their envelope-ceU and running through the cycle of develop- 

 ment of their parent-cells. In passing into the state of rest, the enclosed 

 primordial cell secretes over its surface, inside its. envelope, like every pri- 

 mordial utricle, a new tough cellulose membrane, and through this metamor- 

 phosis assumes the form of an ordinary Protococcus-cell, while the envelope- 

 ceU is dissolved. ^ But only such primordial cells behave in this way as are 

 produced by the division of a Chlannjclococcus-glohule in a lower power of 

 two : the primordial cells originating from a 16-64-fold division move far 

 more actively and do not secrete an envelope-cell ; they are incapable of any 

 propagation, and pass immediately into the condition of rest. Alex. Braun 

 has called these forms of Chlami/clococcus, which develope an envclo23e-cell, 

 macrof/onidia, and distinguished the smaller ones originating from multifold 

 di\asion, as microgonkUa.^' 



The division of the spore- or red resting- cells of ChJamydococcus into two, 

 and then into foui' segments, each producing a new generation of resting- 

 cells, has of late been questioned by Cohn and Wichura ; but Mr. Ciu'rey 

 believes he can confirm this occurrence, since he has " distinctly observed 

 the process of self- division in some red resting- cells, which were probably 

 those of Cldamydococcus. I say," he writes, ^^ prohahly, because the red 

 resting-cells of Cldamydococcus are quite undistinguishable from those of 

 another of the Volvocinece, viz. SteplianospTia?ra pluvialis, so that without 

 following out the development it is impossible to predicate whether such red 

 cells belong to one or the other." (J. M. S. 1858, p. 209.) A further refer- 

 ence to this topic will be found in the account of Stephanosph(xra. 



On reviewing his history of Cldamydococcus (Protococcus) pluvicdis, Cohn 

 attributes to this plant an ' alternation of generations,' and points out the 

 periodicity observed in the appearance in a collection of water of the several 

 phases, the one replacing the other {On Protococcus, R. S. 1853, pp. 549, 550). 

 Subsequently he details the number of very various and changing forms of 

 develojmient it passes through, '^ which have been either erroneously arranged 

 as distinct genera or at least as remaining stationary in those genera, although 

 in fact only transitional stages " (p. 559). " Thus," he continues, " the ' stiU ' 

 Protococcus-ee]l (XIX. 20) corresponds to the common Protococcus coccoma 

 (Kg.) ; when the border becomes gelatinous it resembles P. pidcJier, and the 

 small cells P. minor. The encysted motile zoospores are the genus Gyges 

 granulum among the Infusoria, resembling also on the other side P. turgidus 

 (Kg.), and perhaps P. versatUis (Braun). The zoospores divided into two must 

 be regarded as a form of Gi/ges hipartitus, or of P. dimidiatus. In the quadri- 



