MULTIPLICATION OF PEDIASTREJE. 



271 



extension of its innermost membrane ; whilst seven yet remain in 

 its interior. The new -bom family, as it appears immediately on 



Fig. 116. 



Various phases of development of Pediastrum granulatum. 



its complete emersion, is shown at b ; the gonidia are actively 

 moving within the vesicle ; and they do not as yet show any indi- 

 cation either of symmetrical arrangement, or of the peculiar form 

 which they are subsequently to assume. Within a quarter of an 

 hour, however, the gonidia are observed to settle-down into one 

 plane, and to assume some kind of regular arrangement, most 

 commonly that seen at c, in which there is a single central body 

 suiTounded by a circle of five, and this again by a circle of ten ; 

 they do not, however, as yet adhere firmly together. The gonidia 

 now begin to develope themselves into new cells, increase in size, 

 and come into closer approximation (d) ; and the edge of each, 

 especially in the marginal row, presents a notch, which foreshadows 

 the production of its characteristic 'horns.' "Within about four or 

 five hours after the escape of the gonidia, the cluster has come to 

 assume much more of the distinctive aspect of the species, the 

 marginal cells having grown-out into horns (e); still, however, they 

 are not very closely connected with each other ; and between the 

 cells of the inner row considerable spaces yet intervene. It is in 

 the course of the second day that the cells become closely applied 

 to each other, and that the growth of the horns is completed, so 



