Dr. F. Cohn on a new germs of the famihj 0/ Volvocinese. 337 



^•f I'licture, and, like all forms of Protococcus, consist simply of a 

 tough spherical cellulose membrane and green or red contents 

 organized as primordial utricle. The history of development 

 sjiows that under certain conditions the contents of the motion- 

 l(;ss cells become divided into a number of portions, which always 

 correspond to two, or a power of two in their number ; that these 

 ])ortions become organized into special primordial utricles, and 

 ;(s such break through the parent-cell, each developing two cilia, 

 and by the aid of these rotating actively in the water. During 

 their motion they excrete a delicate cellular membrane over their 

 entire surface, which is gradually removed farther and farther 

 IVom the primordial utricle by endosmose of water, until at length 

 it becomes the wide envelope of the moving form described above 

 (Nachtriige, tab. Q7. A. figs., 23, 35, 29). From this it follows 

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

 of simple cells, but display some peculiarities in their structure 

 and development, since the internal coloured globule corresponds 

 originally to the primordial utricle of other vegetable cells, yet 

 is not surrounded by a membrane, as usual, but suspended free 

 in it like a cell-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 primordial-cell, and the enclosing 

 inembrane with its watery contents the envelope-cell. The moving 

 Chlam?/dococcus- condition is capable of propagating as such, by 

 the enclosed primordial-cell dividing anew, the individual por- 

 tions slipping out of their envelope-cell and running through the 

 cycle of development of their parent-cells. In passing into the 

 state of rest, the enclosed primordial-cell secretes over its surface, 

 inside its envelope, like every primordial utricle, a new tough 

 cellulose membrane, and through this metamorphosis assumes the 

 form of an ordinary Protococcus-cell, while the envelope-cell is 

 dissolved (Nachtrage, tab. 67. B. figs. 91, 92, 93). But only 

 such primordial-cells behave in this way as are produced by the 

 division of a Chlamydococcus-^ohxAe 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 in- 

 capable of any propagation and pass immediately into the con- 

 dition of rest (/. c. tab. 67. A. figs. 56-62, tab. iS7. B. figs. 79, 

 80). Alex. Braun has called these forms of Chlamydococcus, 

 which develope an envelope-cell, mucr-ogonidia, and distinguished 

 the smaller ones originating fi'om multifold division, as micro- 

 gonidia . 



Ann. ^' Mag. N. Hist. Ser. 2. Vol. x. 22 



