336 Dr. F. Cohn on a new genus of the family o/" Volvocinea. 



can discover an essential distinction. I have mentioned in my 

 essay, that Ehrenberg himself, although he claims the moving 

 condition of the forms allied to Chlamydococcus as Infusoria, has 

 declared the resting-stage of this or a most closely allied genus 

 to be an undoubted Alga ; and yet the moving Infusoria are only 

 a propagative form of the motionless Alga. Finally, I have 

 succeeded in demonstrating the membrane of the cells of Chlamy- 

 dococcus both in the resting, and particularly in the moving stage, 

 to consist of cellulose, and thus of establishing the most important 

 criterion of a vegetable cell we are at present acquainted with, 

 the ternary composition of the cell-membrane, in the Infusorioid 

 condition of Chlamydococcus. In fact, all the more recent close 

 observers of Chlamydococcus, the number of whom is not incon- 

 siderable, have almost without exception agreed in recognizing, 

 in all conditions of the development of this form., only a plant and 

 nothing but a plant. 



Although I refer to the essay above cited in regard to the 

 special physiological and developmental characters of Chlamydo- 

 coccus pluvialis, I cannot omit to include here a sketch of its 

 general course of development, because the key to the compre- 

 hension of the Fb/vocme<s generally, and the Step hanosp/uE7'a here 

 described in particular, lies in that remarkable organism, and in 

 it is revealed most clearly the complete conception of their vege- 

 table nature. 



The moving cell of Chlamydococcus is composed of two 

 principal parts, a hyaline spherical envelope, which is formed of a 

 delicate structureless membrane consisting of cellulose, and im- 

 mediately surrounds colourless contents, perhaps consisting of 

 pure water. In the centre of the envelope occurs a coloured 

 globule, composed of the universal nitrogenous protoplasm or 

 mucus of vegetable cells, coloured red or green by chlorophyll or 

 a carmine-red oil, and containing imbedded in it numerous 

 granules of protoplasm, as well as one or more large chlorophyll 

 vesicles. This coloured globule is attenuated at the upper end 

 into a colourless point ; from this go out two cilia, which pro- 

 trude into the water through two orifices in the membrane of 

 the envelope and produce the movements of the whole. The 

 inner coloured globule is not bounded by any rigid membrane, 

 but merely by a thickened layer of protoplasm ; hence its contour 

 is very changeable and passes through manifold transformations 

 in the course of its development. In particular it frequently 

 becomes elongated in all directions into colourless radiating fila- 

 ments, which keep the internal coloured globule suspended freely 

 in the envelope, and are afterwards retracted in the course of 

 the development (vide my Nachtrage, &c. t. 67. A. figs. 27, 28). 



The motionless cells of Chlamydococcus are of much simpler 



