332 EXPLANATION OF THE PLATES. 



double layer. The third, not yet emptied cell, is in the 

 actual transition to the formation of gonidia ; it exhibits 

 the first divison of the contents into two halves, one of 

 which already appears halved again. The arrangement 

 of the sixteen cells of the entire disk is an unusual one, 

 l-j-G-f-9, the outer circle in this case being incomplete, 

 and a cell of the inner circle, opposite the break in the 

 outer circle, possesses one horn. 



Fig. 2. The new-born family, immediately after the 

 birth, seen from the corner. It is derived from the cell 

 a of the disk represented by figure 1. The innermost 

 lamella of the mother-cell has wholly emerged from the 

 old cell as an extremely thin vesicle enclosing the 

 gonidia ; the gonidia in the interior of the mother-vesicle 

 moving actively. 



Fig. 3. The same family, in the same stage, seen on 

 the surface. 



Fig. 4. The same, in a later stage, namely, a full 

 quarter of an hour after birth, in the same position as 

 fig. 2. The gonidia, now at rest, have arranged them- 

 selves in a plane in the plane of section of the equator of 

 the mother-vesicle. 



Fig. 5. The same, in the same stage, showing the 

 surface. The sixteen gonidia, united into a colony, form 

 a circular sixteen-celled disk, in the arrangement 1 + 5 

 -f- 1 ; but they do not adhere firmly together. A slight 

 emargination is already visible on the outside border of 

 the cells. 



Fig. 6. Another young family in the same stage as 

 fig. 5, about half an hour after birth. The arrangement 

 5+11. 



Fig. 7. Another of the same age, exhibiting the 

 arrangement 6-J-10. 



Fig. 8. The families represented in figs. 2, 3, 4, 5, 

 one hour after birth. The emargination of the cells has 

 advanced further. 



Fig. 9. The same again, but four hours after the 

 gonidia ceased to move, (four hours and a half after 



