Dr. F. Cohn on a new genus of the family of Volvocinese. 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 eai-th with dried Stephanosphcera 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 Stephanosphcera 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 Stephanosphar^e, as numerous experiments 

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

 ChlamydococcuSf by rapid desiccation, I believe that the motion- 

 lesis, 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 Stephanosphara, 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 

 Stephanosphcera-sip}ieres 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 Volvocinea, 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 Stephanospharcp, 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- 

 sphcens 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 Chlamy- 

 dococcus and scarcely any Stephanosplicera ; 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 pubhcation in this form and not revised by myself ; they con- 

 tain many and essential inaccuracies. 



