MULTIPLICATION OF DESMIDIACEJE. 



271 



composed of either of the just mentioned multiples or sub-mul- 

 tiples of that number. At A is seen an old disk, of irregular 

 shape, nearly emptied by the emission of its gonidia, which had 



Various phases of development of Pediastrum granulatum. 



been seen to take place, within a few hours previously, from the 

 cells a, &, e, d, e; most of the empty cells exhibit the cross slit 

 through which their contents had been discharged; and where 

 this does not present itself on the side next the observer, it oc- 

 curs on the other. Three of the cells still possess their colored 

 contents, but in different conditions. One of them exhibits an 

 early stage of the subdivision of the endochrome, namely, into 

 two halves, one of which already appears halved again. Two 

 others are filled by sixteen very closely crowded gonidia, only 

 half of which are visible, as they form a double layer. Besides 

 these, one cell is in the very act of discharging its gonidia; nine 

 of which have passed forth from its cavity, though still enveloped 

 in a vesicle formed by the extension of its innermost membrane; 

 whilst seven yet remain in its interior. The new-born family, 

 as it appears immediately on its complete emersion, is shown at 

 B; the gonidia are actively moving within the vesicle; and they 

 do not as yet show any indication either of symmetrical arrange- 

 ment, 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, surrounded by a circle of five, and 

 this again by a circle often; 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 approxima- 

 tion (D) ; and the edge of each, especially in the marginal row, 

 presents a notch, which foreshadows the production of its charac- 



