Dr. F. Cohu on a new genus of the family of Volvocincge. 405 



living after being dried up for years and are capable of giving 

 birth to moving forms, while the swarming-cells themselves are 

 destroyed for ever by rapid desiccation. Herr von Flotow has 

 sent earth with dried StephanospharcB to Dr. Rabenhorst in 

 Dresden, who, in like manner, succeeded in reviving them by 

 moistening; in this way the latter obtained abundant material 

 for distributing Stephanosphm-a under No. 102 of the 11th De- 

 cade of his ' Algen Sachsens resp. Mitteleuropas/ and thus to 

 effect the more general diffusion of this remarkable organism*. 



Since the moving Stephanosph(F>'(B, as numerous experiments 

 have taught me, are destroyed, just like the swarming-cells of 

 Chlamydococcus, by rapid desiccation, I believe that the motion- 

 less, Protococcoid globes, the development of which I have just 

 described, are the forms which do not lose their vitality by dry- 

 ing, but are capable, when wetted again with water, of going 

 through a cycle of development, by which they return to the 

 normal moving form of Stephanosphcera. Yet I must remark 

 that I have not hitherto obtained sufficient material to observe 

 the resting Stepkanosphcera, and to trace the processes which 

 occur in the revivification, and that in reference to this most im- 

 portant phsenomenon I must leave a gap, which I hope to fill up 

 next summer. 



In conclusion I add a note on the mode by which I have 

 succeeded in obtaining sufficient material for my observations, 

 since this also is of physiological interest. At their stations the 

 StephanosphcBra-SY>heves occur mingled with Chlamydococcus^ but 

 by no means in the abundance requisite for the investigation ; 

 and although green clouds do collect at certain points in the 

 water wholly composed of our Volvocinece, it is difficult to ex- 

 tract sufficient of them for examination, since they immediately 

 start apart when touched. I succeeded in overcoming this in- 

 convenience by a simple means, so as to bring thousands of 

 these elegant organisms on to the object-holder at any moment. 

 I took, namely, a flat bottle with a short narrow neck, and nearly 

 filled it with the water containing StephanospJuBra, stopped it 

 with a cork, and then laid it horizontally so that the cork partly 

 dipped in the water. In a few hours almost all the Stephano- 

 sphcBra in the water collected on the cork, which was covered 

 with a green coat composed exclusively of the revolving spheres, 

 while the rest of the water in the bottle contained only Cldamy- 

 dococcus and scarcely any Stephanosphara ; so that when I wished 



" I must observe, however, that some of the specimens compared by 

 myself contained no Stephanosphara. A few printed details are given with 

 the specimens, gathered from information furnished in my letters, not in- 

 tended for publication in this form and not revised by myself j they con- 

 tain many and essential inaccuracies. 



