Dr. F. Cohn on a new genus of the family of Volvocinese. 409 



generation which becomes permanent, the secondary-cells pro- 

 duced by the multifold subdivision separate from each other ; 

 they are smaller, spindle-shaped, and bear four cilia, by means of 

 which they move very actively, even inside the parent envelope, 

 and after breaking out of this, move freely and singly through 

 the water, without ever secreting an envelope-cell, and giving 

 rise to the production of a family of cells. 



10. At certain times the individual primordial-cells develope 

 a special membrane inside their envelope-cell, closely enclosing 

 them ; they then break away, move at first in the intei-ior of the 

 envelope, and finally emerge free into the water as Chlamydo- 

 monas-\\VQ globes; after a short swarming these pass into a Pro- 

 tococcoid condition of rest. 



11. It is probably this resting condition which alone of all 

 the forms of development of StephanosphijEra possesses the power, 

 after being dried up from water, of being revived by a new ad- 

 dition of watei', and causing the origin of new moving genera- 

 tions ; but the process here in question has not yet been com- 

 pletely observed. 



12. The StephanospharcB avoid both bright light and complete 

 darkness ; they seek moderately lighted spots and half- shadow. 



13. The organization and development of Stephanosphara 

 agree essentially with those of Clilamydococcus pluvialis, the ve- 

 getable nature of which has been placed beyond doubt by recent 

 researches. The only distinction consists in the type of the 

 latter genus being represented by a simple cell, while that of 

 Stephanospluera and the rest of the Volvocinece is represented by 

 a family of cells. 



14. The mode of propagation by micro- and macrogonidia in 

 Stephanosphara exhibits the most unquestionable analogies with 

 an evident plant, Hydrodictyon utriculatum, and testifies to the 

 near relationship of the two genera. 



15. All the other Volvocinece, as well as Stephanosphcera, are 

 to be regarded as plants, and their organization can be under- 

 stood and judged of naturally only according to analogy with 

 vegetable cells. 



EXPLANATION OF PLATE VL 



Fig. 1. Polar view of a Stephanosphcera with large globular primordial- 

 cells. 



Fig. 2. The same in the equatorial view, the points of the primordial-cells 

 run out into mucous filaments. 



Fig. 3. Polar view of a Stephanosphara with eight smaller, distantly placed 

 primordial-cells : a, envelope-cell ; b, b, primordial-cells. 



Fig. 4. The same in the equatorial view ; the primordial-cells running out 

 into variously ramified raucous filaments ; the two front (interior 

 in the figure) ones exhibit the points from which the cilia arise. 



