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



IX. On the Physiology of Stephanosphsera. 



That the formation of macro- and microgonidia does not ex- 

 haust the whole series of forms which Stephanosphara may pass 

 through is proved by the following observation^ which unfor- 

 tunately I have not yet been able to complete. Having culti- 

 vated some Stephanosph(Era for a long time in a little glass cup, 

 in the way described in my essay on Loxodes Bursaria {l. c), all 

 the primordial-cells at length exhibited dark, thick, greenish 

 brown contents, so densely filled with numerous granules that 

 the two chlorophyll-vesicles could no longer be detected; their 

 form was more or less globular, and the mucous radiating 

 processes were entirely absent ; their outlines were remarkably 

 sharply defined, as if they had become surrounded by a rigid 

 membrane. At the same time I remarked that the primordial- 

 cells were no longer fixed immoveably at the periphery of the 

 envelope-cell, never changing their relative positions; hui jerked 

 backwards and forwards, finally tore themselves away from the en- 

 velope-cell, and then began to rotate slowly and lazily in the infe-- 

 rior. 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 independent globes ; they were now seen to 

 be enclosed in a pretty closely applied envelope, fhrough which 

 penetrated two cilia, and hence they present the utmost resem- 

 blance to Chlamydomonas Pulvisculus (fig. 20). They moved 

 about for some time in the water and at length came to rest, 

 losing their cilia and accumulating like little green Protococcus- 

 globules at the bottom of the glass. We therefore have here a 

 motionless, perfectly plant-like stage of Stephanosphara, such as 

 we are acquainted with 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 water of ditches is dried up in summer. The emergence of 

 single globes from the common envelope, in a form resembling 

 Chlamydomonas, may also be readily observed in Gonium (Ehr. 

 Infusor. pi. 3. fig. 1). 



I conjecture that the motionless, Protococcoid cells of Stepha- 

 nosphcera are the means for the preservation of the species when 

 the water, as is always the case in the shallow hollows in stones, 

 their natural station, is dried up for a long time and all the 

 living inhabitants are precipitated on the stone. The observa- 

 tions of Major von Flotow have already demonstrated that the 

 dried-up muddy sediment always reproduces ^tephanosphcRrce 

 when water is again poured on to it. This capability^ of reviving 

 from the dried condition, is shared by Stephanosphcsra with Chla- 

 mydococcus pluvialis, in which likewise the motionless cells remain 



