176 GENERAL HISTORY OP THE INFIISOEIA. 



Soon after, I saw the envelope-cell also burst at some spot and collapse ; and 

 the eight primordial cells gradually emerged, one after another, as inde- 

 pendent globes : they were now seen to be enclosed in a pretty closely applied 

 envelope, through which penetrated two cilia ; and hence they presented the 

 utmost resemblance to Chlcnnydomonas Pidviscidus. They moved about for 

 some time in the water and at length came to rest, losing their cilia and accu- 

 midating like Utile green Protococcus-glohides at the bottom of the glass. We 

 therefore have here a motionless, perfectly plant-like stage of Stephanosphcera , 

 such as we are acquainted -^ith in Chlamydococcus and Chlamydomonas ; the 

 remainder of the Volvocinece undoubtedly pass into a similar condition of 

 rest, which is the means of their preservation when the Avater of ditches is 

 diied up in summer. The emergence of single globes from the common enve- 

 lope, in a form resembling Chlamydomonas, may also be readily observed in 

 Goniimi. 



'' I conjecture that the motionless Protococcoid ceUs of Stephanospho'.ra are 

 the means of the presei^ation of the species when the water, as is always 

 the case in the shallow hollows in stones, their natural station, is diied up 

 for a long time and all the living inhabitants are precipitated on the stone. 

 The observations of Major von Flotow have already demonstrated that the 

 dried-up muddy sediment always reproduces StephanosphcBrcE when water is 

 again poured on to it. This capahility of reviving from the dried condition 

 is shared hj Stephanospha^ra Avith Chlamydococcus pliivialis,Yn. which likewise 

 the motionless cells remain living after being diied up for years, and are capa- 

 ble 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 htephanospha'rce to Dr. Rabenhorst in Dresden, who, in like manner, 

 succeeded in reviving them by moistening. 



" Since the moving Stephanosj^hcera? are destroyed, just like the swarming- 

 cells of Chlamydococcus, by rapid desiccation, I believe that the motionless 

 Protococcoid globes, the development of which I have just described, are the 

 fonns which do not lose their vitality by diying, but are capable, when wetted 

 again with water, of going through a cycle of development, by which they 

 return to the normal mo\T.ng form of Step>hanosphcera, Yet I must remark 

 that I have not hitherto obtained sufficient material to observe the resting 

 Stephanosphcera, and to trace the processes which occm^ in the revivification. 



*' Respecting their vital manifestations, repeated experiments showed that 

 the moving spheres of Stephanosphaera seeh the darlcer part of the vessel, avoid- 

 ing however a total absence of light, and assembling in preference in a moderated 

 light or half-shadoiv. Since other Algse and Infusoria exhibit a different 

 beha\doui' towards the light, we thus possess a means of sorting, to a cer- 

 tain extent, the microscopic inhabitants of a specimen of water, as I did the 

 shade-loving Stephanosphcerce from Chlamydococcus, which ordinarily seek the 

 brightest light." 



An important appendix to this histoiy of Stephanosphcera has quite recently 

 appeared from the joint labours of Professor Cohn and Wichura {Nov. Act. 

 Acad. Curios. Natures, 1857, Part I.), and has been translated into English 

 by Mr. Currey {J.M.S. 1858, p. 131). 



The resting- stage above spoken of is again referred to concisely and clearly 

 in this paragraph : — " Under ceriain circumstances each of the eight cells 

 secretes a cellular covering, and swims about in the interior of the globe in 

 the form of free Chi amijdomonas -like cells (XIX. 44) ; eventually they escape, 

 either by fissm'e of the globe, or by its gradual dissolution, lose their cilia, 

 form a thicker membrane, become motionless, and accumulate at the bottom 

 of the vessel. If the vessel be then permitted to become thoroughly diy, and 



