344 Dr. F. Colin on a new genns of the family 0/ Volvocineee. 



movement of the eight small wheels rotating in the interior of 

 the common envelope-cell, vi^hich constitutes a very pretty object, 

 the parent-cell soon becomes enlarged and attenuated at certain 

 points ; the cellulose of which it is composed appears to be trans- 

 formed into soluble jelly, and soon afterwards one after the other 

 breaks through out of the common envelope and revolves freely 

 and independently in the water, according to the same laws as 

 the old spheres, but more actively and energetically. The young 

 StephanospJmra exactly resembles a green wreath composed of 

 eight small cylinders, upon which by itself no envelope and cilia 

 can be detected (fig. 13) ; but if killed with iodine, the eight 

 primordial- cells are seen to be surrounded by a common envelope- 

 cell in the form of an exceeding delicate membrane; only this 

 lies in all parts almost immediately upon the green globes, so 

 that it follows the waved outline they produce, and in its total 

 form resembles a flat spheroid with eight notches on its border ; 

 it is perforated by the cilia, which go off in pairs from each of 

 the primordial-cells ; and two chlorophyll-utricles are already 

 distinguishable in the latter (fig. 14). By degrees the envelope- 

 cell is lifted up by the endosmotic absorption of water ; its sur- 

 face becomes smoothed out, and it appears circular in the polar 

 view ; on the other hand, it retains for a longer time the form of an 

 almost tabular spheroid, and hence presents an ellipse in the equa- 

 torial view (fig. 15); finally it expands uniformly in all direc- 

 tions and thus acquires its normal spherical form, while at the 

 same time it becomes considerably thickened. This whole pro- 

 cess of propagation is completed during the night, and on bright 

 days StqjhanosphcErce are rarely seen in course of division at sun- 

 rise ; on dull days they may be observed in this condition in the 

 first part of the morning. 



The primordial-cells, however, not unfrequently come to a 

 standstill in the stage of division of the second generation, so 

 that they only separate into four secondary-cells ; these at once 

 develope cilia and an envelope- cell, without dividing a third time, 

 and make their exit from the parent-envelope in this condition. 

 Here therefore only the first generation of each primordial-cell 

 is a transitional generation, the second already a permanent gene- 

 ration. Hence arises the circumstance that we often find among 

 other eightfold Stephanosphai^a-glohes, some in which the en- 

 velope-cell encloses only four primordial-cells standing at equal 

 distances, which in other respects behave in the ordinary man- 

 ner (fig. 7). 



It is still more frequently observed, when the primordial-cells 

 have already become constricted into four secondary cells and 

 are beginning to divide again into eight, that this process of 

 division is not perfectly completed in all four portions, but that 



