OF THE PHTTOZOA. 169 



Cniptomonadina, kc), and which certainly do not bear at all the character of 

 piu'posing, conscious volition, but appear as an activity determined not indeed 

 by pui-ely external causes, but by internal causes in the organization and vital 

 process. The collective idea of such motions is best represented by the coui'se 

 described by a top which runs thi^ough the most varied cui'ves while at the 

 same time constantly revohing on its axis. 



" Although Alex. Braim describes a constant revolution to the left in the 

 in many respects analogous swarming- cells of Chlamydococcus and the swarm- 

 ing- spores of (Edogonium, and to the right in the moving gonidia of Vaiicheria 

 and the families of Pandorina, I must assert that no such constant Jaw of re- 

 volution exists in the structure here described. 



"As to its systematic position. — It is evident that the organism tve have 

 described belongs to the family of the Volvocinew. For not only do we find in 

 it the two principal characters which are characteristic of this interesting 

 family — the presence of a number of green globes which, enclosed in a 

 common coloiuiess envelope, represent a family of cells (polypidom), together 

 with the constant rolling motion which the Volvocinece possess through 

 almost the whole of their life, — but oui' form also displays, as Ave shall see 

 hereafter, the thii^d character of the Volvocinece, that the separate globes propa- 

 gate within the envelope. In fact, there exist the greatest analogies between 

 the knoA\Ti genera of Volvocinece, especially Gonium and Pandorina, and the 

 organism here described ; and these genera are only essentially distinguished 

 by the aiTangement of the green globes or primordial cells, which in Pando- 

 rimi are placed on a spherical surface, in Goyiium on a flat plane, while in 

 our form they stand at the cii'cumference of a circle. Since, however, this 

 very law of arrangement is, in the family of the Volvocinece, the most im- 

 portant criterion on which the establishment of the genera depends, it follows 

 that we here have a peculiar genus which I do not find described either in 

 Ehrenberg's great work or in any later publication. 



" If we now compare the conditions of organization of Stephanosphcera 

 Arith those of Chlamydococcus, we find the most essential agreement. In the 

 fii'st place the envelope-cell of Stephanosphcera corresponds exactly to that of 

 the moving macrogonidia of Chlamydococcus ; it is composed of a delicate 

 colourless membrane and contents resembling water. Chemical actions to 

 which I subjected the envelope- cell of Stephanosphcera, bear Avitness of tliis 

 agreement in the most minute particulars. The envelope-cell is indiflferent 

 to acids and alkahes and is not dissolved in them ; but it suffers a peculiar 

 thickening by sulphuiic acid, which causes it to apply itself more closely to 

 the primordial cell, and present itself very distinctly and clearly defined. In 

 general the application of dilute sulphuric acid is often the best means of 

 making clear delicate vegetable membranes wliich would otherAAise be readily 

 overlooked, especially Avhen iodine is added, Avhich then ordinarily colours the 

 membrane yellow. The cilia also are rendered more distinct by sulphuric 

 acid. The envelope-cells of Pandorina, Chlamydococcus, and Volvox behaA'e 

 in exactly the same Avay. 



" AVith regard to the chemical composition of the envelope-cell of Stepha- 

 nosphaTa, I have succeeded in demonstrating the characteristic reaction of 

 vegetable celhdose, the blue colouring by iodine and sulphuric acid, in the enve- 

 lope-cell of Stephanospha^ra. For this piu'pose it is requisite to aUoAV a drop 

 oi pretty concentrated sulphuric acid to act upon the swarming Stephanosphcera- 

 globes imtil the green primordial cells in the interior are decomposed, — by 

 wliich time the proper transformation of the envelope-membrane has taken 

 place, and a drop of solution of iodine (iodine in iodide of potassium), suffi- 

 ciently diluted to prevent the sulphuric acid precipitating it in crystals, then 



