CELLS OF BACILLUS MEGATHERIUM 69 



not enough so to be of great significance. In the second colony only 

 one of the inoculated cells grew; the others actually decreased some- 

 what in size. We have again a long lag period in the curve for cell 

 size, during which they actually decreased somewhat. In the third 

 micro-colony the changes in cell size are not nearly so pronounced. 

 It will be remembered that this colony started from five cells, of 

 which three grew, and as will be seen later, the tendency is for the 

 change in cell size to be less with increased seedings. 



From these micro-colonies we may draw the following tentative 

 conclusions. The increase in number of cells is accompanied by an 

 increase in size. This is apparently more marked with the small 

 seeding (first colony, starting from two cells) than with the larger 

 seeding (third colony, developing from five cells). The lag period 

 before the beginning of cell multiplication is not entirely occupied by 

 a transformation of the mature cells to large growing cells. There 

 is also a lag phase in the curves for cell size. Not all of the cells 

 respond equally to the new medium, some remaining dormant for 

 considerable periods of time. There does, therefore, occur a selec- 

 tion of a rapidly growing strain in some cases. The cells which remain 

 dormant may continue to change in morphologic characters as they 

 would have if they had remained in the old medium, becoming smaller 

 in size, distorted in form, or dying and disintegrating. 



Further studies have been made in a culture grown on agar 

 slants (designated Culture I in the tables), following the technique 

 described in Chapter III. The agar slant tubes were inoculated 

 from an agar culture which had been transferred every twelve hours 

 for several days to get rid of spores, since it was desirable to study 

 the morphologic variations during the early stages of growth uncom- 

 plicated by spore germination. In all of these studies of B. megather- 

 ium the cultures used for seeding were free from spores as far as 

 could be determined by microscopic examination. Samples were 

 removed every half hour for the first twelve hours of growth, every 

 hour for the next twelve hours, every four hours for the second 

 twenty-four-hour period, and again at sixty and seventy-two hours. 

 Cell counts were made beginning with the first half-hour period, 

 and are presented in Table VI. The number of free spores was 

 observed aftd bjjore formation commenced, and is recorded in the same 



