408 Dr. F. Cohn on a new genus of the family of Volvocincasf. 



2. It is formed of eight equivalent green primordial-cells, which 

 are arranged at the circumference of a circle ; these are enclosed in 

 a common envelope-cell, in which they stand at the equator, near 

 the circumference. h 



3. The envelope-cell is of perfectly spherical form, and is com- 

 posed of a structureless, completely closed cellulose membrane, 

 filled with limpid contents (water?). 



4. The eight primordial-cells are globular, cylindrical or 

 spindle-shaped, and are composed of the universal nitrogenous 

 protoplasm of vegetable cells, which is coloui-ed green by chlo- 

 rophyll, and rendered opake by numerous fine granules (starch 

 or protoplasm ?) ; they ordinarily enclose two chlorophyll-utricles 

 containing starch. They are not bounded by any rigid mem- 

 brane. 



5. The substance of the primordial-cells becomes prolonged, 

 especially at the two ends, into radiating and often ramified mu- 

 cous filaments, which are retracted in the course of vegetation ; 

 the protoplasm-filaments occur also in other Volvocinece, and have 

 been difi'erently interpreted in them (as hairs, tails, a vascular 

 system, intercellular passages, &c.). 



6. Each primordial-cell bears two ciha at the point turned 

 outwards, and these penetrate, through orifices in the envelope- 

 cell, into the water, and cause the movement of the entire orga* 

 nism. '"3 



7. The laws of the movement agree with those of the swarming- 

 cells of Algae, and Astomous or Anenterous Infusoria ; it con- 

 sists of a rapid rotation round the axis of the envelope-cell, which 

 does not take place in any given direction, and of a simultaneous 

 screwing forward, by which the Stephanosphcsra runs through 

 manifold curves in different planes. 



8. The propagation takes place by division of the primordial- 

 cells inside the envelope-cell. Each primordial- cell separates, by 

 successive septa, first into two, then into four, and lastly into 

 eight secondary cells ; from this last division proceeds a perma- 

 nent generation, while the two preceding were only transitional 

 generations ; the eight secondary-cells originating from one pri- 

 mordial-cell arrange themselves at the circumference of a circle, 

 each developing two cilia, and remain united, secreting a com- 

 mon envelope over their surface, which, at first appressed and 

 tabular, becomes removed away and acquires a spherical form 

 through absorbing water. In this propagation by macrogonidia 

 eight exactly similar young Stephanosph(jer(B originate in each 

 envelope-cell of the parent organism. More rarely, the second 

 division forms a permanent generation, and then the envelope- 

 cell contains only four primordial-cells. 



9. In the propagation by microgonidia, which commences in 

 a similar manner, when however it is only the sixth or seventh 



