Dr. F. Cohn on a new genus of the family of Volvocinese. 329 



chiefly into one hemisphere of the envelope- cell. In this way we 

 possess at least the possibility of making out whether the revo- 

 lution takes place to the right or to the left. But in both cases 

 it is found that the rotation of the envelope-cell is not at all 

 constant in one direction ; for not only do different spheres re- 

 volve some to the right and others to the left, but even one and ' 

 the same individual rotates for a time with striking rapidity 

 towards the right, the rapidity gradually slackens, the globe 

 rests for a moment, and the moment after it revolves towards 

 the left, with gradually increasing rapidity, and after some time 

 the rotation returns again in a similar manner to its revolution 

 toward the right. Although, therefore, Alex. Braun describes a 

 constant revolution to the left in the in many respects analogous 

 swarming-cells of Chlamydococcus and the swarming-spores of 

 (Edogonium, and to the right in the moving gonidiaof Vaucheria 

 and the families of Pandorina*, I must assert, that no such con- 

 stant law of revolution exists in the structure here described^. 



III. Systematic Position. 



In the foregoing pages I have confined myself to the simple 

 description of the observed forms, without raising the question 

 of the place which the organism here characterized occupies in 

 the series of known beings, — in what genus, what natural family 

 it is to be arranged ; nay, above all, in which kingdom of nature it 

 is to be enrolled as a citizen. The settlement of these questions 

 is requisite before anything else, in order to ai-rive at an actual 

 comprehension of the parts just described. 



It is soon seen that it is easier to establish the nearest rela- 

 tionship, particularly the natural family, than to decide the 

 question whether we have to do with an animal or a plant. It 

 is evident at once, namely, that the organism we have described 

 belongs to the family of the Volvocinece. For not only do we find 

 in it the two principal characters which are characteristic of this 

 interesting family ; the presence of a number of green globes, 

 which, enclosed in a common colourless envelope, represent a 

 family of cells (polypidom), together with the constant rolling 

 motion which the Volvocinece possess through almost the whole of 

 their life, — but our form also displays, as we shall see hereafter, 

 the third character of the Volvocinece, that the separate globes 

 iropagate within the envelope. In fact, there exist the greatest 



lalogies between the known genera of Volvocinece, especially 



Ueber die Verjungung in der Natur, p. 227. 

 t According to my observations, an alternation of the direction of ro- 

 tion occurs in Chlamydococcus pluvialis similar to that which I have 

 tscribed above (vide Nachtrage, &c. I. c. p. 73fi). 



