410 Dr. F. Cohn on a new genus of the family q/* Volvocinese. 



Fig. 5. Equatorial view as in fig. 4 ; the primordial-cells are more crowded 

 into one hemisphere of the envelope-cell. 



Fig. 6. Polar view ; only six primordial- cells exist, but the upper two are 

 twice as large as the others. 



i^i 7»' Pola^^ view; the envelope-cell contains only four primordial-cells, 

 the product of the second division having become a " permanent 

 generation." , 



Fig. 8. Commencement of the formation of macrogonidia ; the primordial-^ 

 cell * is still unaltered ; the cell ** exhibits a flow of the content^ 

 * ' towards the two ends ; the primordial-cell in the middle has di- 

 t(>i c,!/ 4 vided into two, the rest already into four secondary cells. 



.^j^r^f-All the eight primordial-cells have divided, in the fom- secondary 

 cells of the second "transitional generation." 



Fig. 10. The division already advanced to the third " permanent generi^-.^ 

 tion," so that each primordial-cell has separated in eight wedgd- 

 shaped pieces. 



Fig. 11^ -The young Stephanosphcerce produced by the division have become 



_^v„ • more organized, the colourless connected mass of protoplasm in 



the middle having been gradually constricted and cut off; they 



^['^^ already begin to move inside their envelope : at a, two are seen iti^ 



•it'' the side view. -i^ 



Fig. 12. The division completed and the eight young Stephanosphcerce r^v 

 tating in the common envelope. iy\ 



Fig. 13. A young Stephanosphcera just emerged; its cilia are only visible 

 by the eddy they produce in the w^ater. 



Fig. 14. A similar one kdled by iodine, in the polar view ; it exhibits the 

 cilia and the common envelope-cell which is closely applied to 

 the periphery of the primordial-cells. 



Fig. 15. A somewhat older Stephanosphcera ; the envelope-cell still has the' 

 form of a flat, tabular spheroid, and therefore appears as an ellipse 

 in the equatorial view. 



Fig. 16. Commencement of the formation of microgonidia ; the eight pri- 

 mordial-cells dividing in a higher power of two. 



Fig. 17. The eight original primordial-cells have been broken up into their 

 microgonidia, which swarm about in the common envelope. 



Fig. 18. The same stage as in fig. \7 ; one primordial-cell, a, has taken on 

 the formation of macrogonidia and become developed into a 

 young Stephanosphcera, which rolls along among the crowd of 

 microgonidia. 



Fig. 19. A few microgonidia after their exit from the envelope-cell : a, mo- 

 ving actively in water ; the rest killed with iodine and exhibiting 

 four cilia. 



Fig. 20. A primordial-cell, which after secreting a special coat in a Chla- 

 mydomonas-like condition, has emerged from the common en- 

 velope-cell to pass subsequently into a state of rest. 



Fig. 21. Diagram to illustrate the laws of division in the macrogonidia of 

 Stephanosphcera; first the septum a, m, h, n, is formed, then the 

 second through c, m, d, n, — these two generations are " transi- 

 tional ;" the eight cells produced by the septa h, m, g, n and e, m, 

 f, n, become a " permanent " generation. 



The figures are represented magnified 300 times, except fig. 19, which 

 is 600 times. " '"^' - 



^■■'-^' ..^ 



