AND INHERITANCE IN PEDIASTRUM. 



417 



marily affect the outline of the colony or the arrangement of the 

 cells in concentric series about a center, the displacement being 

 largely in the position of the major axes of the individual cells. 

 This is illustrated as noted in colony 67 (Fig. 25). The second 

 results in an abnormal form for the colony as a whole and the loss 

 of the concentric arrangement of the cells (Figs. 26 and 28). The 

 two types are more or less combined, of course, in the majority 

 of cases. 







27 



Fig. 26. Pediastrtim asperum. Colony irregular, crescent-shaped form. 

 X about 425. 



Fig. 27. P. asperum. Colony fairly regular in outline but interior cells 

 very irregularly placed. X about 275. 



Fig. 28. P. asperum. Irregular colony, somewhat triangular in outline, 

 X about 425. 



The most extreme case of the first type which I have observed 

 is seen in the thirty-two-celled colony (Fig. 27). Here almost all 

 the interior cells are anomogenous in their position and interrela- 

 tions with their neighbor cells, though there is the common general 

 arrangement for a thirty-two-celled colony ; one in the center, six 

 cells in series II., ten cells in series III., and fifteen cells in series 

 IV. All the cells of the outer series are normally placed with long 

 spines outward and the general outline of the colony is circular, but 

 the interior cells are in absolute confusion, as compared with the 

 typical arrangement. Only three cells of series III. have their long 

 lobes radially outward and their long axes tangential and these three 

 are not in normal contact relations with the cells of series II. This 

 colony emphasizes the existence of the stage described under the 

 head of reproduction, where it was noted that the cells of the pe- 

 ripheral series seem to get their definitive positions first while the 



