Dr. F. Cohn on a new genus of the family of Volvocineae. 339 



in Chlamydococcus, is the most evident proof that the organisms 

 to which they belong cannot be regarded as Infusoria, but are 

 sunply Algae. Moreover this behaviour of the envelope-cell of 

 Stephanosph(B7'a shows that the latter is bounded by a true 

 cellulose membrane, and not, as is assumed almost universally 

 of the Volvocinece, and by Nageli even of all Algae, of secreted 

 mucus or jelly*. The direct observation of the envelope-cell of 

 Stephanosplicera likewise shows that this is completely closed in 

 its normal condition, and only perforated by orifices in the spots 

 where the cilia of each primordial-cell pass out. Not until a 

 later stage, when the primordial-cells singly leave the envelope 

 or have begun to progagate, does the membrane of the envelope 

 tear, gradually collapse and become dissolved, so that the included 

 globes can make their exit freely. 



It is obvious that the eight green globes of Stephanosphcera 

 correspond exactly to the primordial-cell of Chlamydococcus. The 

 primordial-cells of Stephanosphcera consist in like manner of 

 nitrogenous protoplasm, in itself colourless, which is coloured 

 brown by iodine and almost wholly dissolved by caustic potash 

 and ammonia. The protoplasm is coloured by the universal 

 colouring matter of vegetables, chlorophyll; for alcohol and aether 

 bleach the green globules, and concentrated sulphuric acid 

 changes the green colour into a verdigris-green or blue — a re- 

 action which, from my observations, is characteristic of chloro- 

 phyll (vide my essay on Loxodes Bursaria, Siebold and Kolliker's 

 Journal, iii. 264). 



The chemical nature of the fine granules in the primordial- 

 cells which with age multiply, so that the primordial-cells at 

 length lose their transparent green colour and appear dull, 

 opake and olive-brown, is difficult to determine on account of 

 their small size ; they are eiihex jjrotoplasm-granules, or, as a bluish 

 colour given by iodine might lead one to conclude, perhaps 

 starch-granules. On the other hand, the two darker nuclei in 

 each primordial-cell are undoubtedly the same structures which 

 occur in Chlamydococcus, and in like manner not only in all the 

 Volvocineae, but also in most of the Algae of the orders of Pal- 

 mellea, Desmidieee, Conferveoi, &c. Nageli has called these chlo- 

 rophyll-utricles, and demonstrated their universal occurrence in 

 the vegetable kingdom by comparative descriptions (Gattungen 

 einzelliger Algen, ii.). Ordinarily there exist only two in Ste-^ 

 phanosjjhara, which may be distinguished in the earliest stages, 

 while among other Volvocinece, for instance, Gonium contains only 

 one chlorophyll-utricle. It is difficult to settle anything definite 



* The common envelope of Gonium is certainly composed of a gelatinous 

 substance without a bounding cellulose membrane. 



32* 



