170 GENERAL HISTORY OF THE INFUSORIA. 



produces a coloration of the envelope, -which appears at first violet, gradually 

 becoming moi'e intense, and at last heautifid indigo-blue. xThus the chemical 

 beha\^our of the envelope-cell in Stej)hanosj)ha?ra, as in Chlamydococcus, is 

 the most evident proof that the organisms to which they belong cannot be 

 regarded as Infusoria, but are simply Algae. Moreover this behaviour of the 

 envelope- cell of Stejyhanosjyhcera shows that the latter is bounded by a tiTie 

 cellulose membrane, and not, as is assumed almost universally of the Volvo - 

 cineoe, and by Niigeli even of all Algae, of secreted mucus or jelly. The direct 

 observation of the envelope-cell of Steplianosjylicera like"^ise shows that this 

 is completely closed in its normal condition, and only perforated by oiifices 

 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 propagate, 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 Steplianosplioira correspond 

 exactly to the primordial cell of Chlamydococcus. The primordial cells of 

 StephanosphcBra consist in like manner of nitrogenous protoplasm, in itself 

 coloiuiess, 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 reaction which, from my observations, is cha- 

 racteristic of chlorophyll. 



" 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 deter- 

 mine on account of theii' small size ; they are either protoplasm-granules, 

 or, as a bluish colour given by iodine might leave one to conclude, perhaps 

 starch-granules. On the other hand, the two darher nuclei in each pri- 

 mordial cell are undoubtedly the same stnictm^es which occur in Chlamy- 

 dococcus and, in like manner, not only in all the Volvocinece, but also in most 

 of the Algae of the orders of Palmellece, Desmidece, Gonfervece, &c. IN'ageli 

 has called these chlorophyll-utricles, and demonstrated their universal occur- 

 rence in the vegetable kingdom by comparative descriptions (Gattung. einzell. 

 Alg. ii.). Ordinarily there exist only two in Stephanosphoira, 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 concerning theii' structure and function ; they must not be 

 regarded as ceU-nuclei, although they resemble them very much, especially 

 when only one is present. Caustic potash, which destroys the rest of the 

 contents of the primordial-cells, makes the chlorophyll utricles of Stepha- 

 nosphoira show themselves more distinctly as hollow rings, surrounded by a 

 membrane which is rather granular ; iodine colours them deep violet, which 

 leads to the conclusion of the presence of starch. Ehrenberg thought the 

 chlorophyll-utricles were to be recognized as the testes of the Volvocinece ; it 

 is certain, however, that these structui-es may be seen in greater or less 

 number, in exactly the same way, in undeniable plants, such as HydrocUc- 

 tyon, (Edogonium, Mougeotia, and others. 



^' I have already shown that the primordial cells of Stephanosphcera as well 

 as those of Chlamydococcus are destitute of a special rigid membrane ; con- 

 sequently they do not correspond to perfect cells, but on the whole only to 

 primordial utricles. In like manner the cmious colourless mucous filaments 

 which extend out from the extremities of the primordial cells of Stepha- 

 nosphcera are evidently analogous to the rays which make one condition of 



