18 Bacterial Disease of the Mango 



several of these long filaments in fairly active motion. Some of the 

 longest ones are swollen irregularly and might perhaps be classed as 

 c involution forms.' They are again mentioned later under this heading. 

 The following are some measurements of such filaments from a 

 preparation made from a three days' old nutrient broth culture con- 

 taining 8-5 % NaCl. 



32/x x 9m - -Qfi 1-9/x x -6yu 



12-6/j. x '6/u. 16//. x •6/x. 



5-9/x x -dfj. 50/j. x -9/x 



In cultures containing 7 % NaCl, the majority of the rods did not 

 exceed 15/x in length, but in the higher percentages there were large 

 numbers of very long filaments. 



Fission. 



The method of fission was studied in an agar hanging block culture 

 (1, p. 110). The smear on the block was made from a suspension in 

 water of a four days' old culture in 2 % dextrose broth. During the 

 observations the rods were exposed to a brilliant light from a Nernst 

 microscope lamp. The temperature of the room was 25° C, but in the 

 vicinity of the microscope varied from 27° to 30° C. owing to the heat 

 from the lamp before mentioned. The lenses used were T V mm. Zeiss 

 immersion and No. 12 compensating ocular ; with these the changes in 

 the shape and grouping of the organisms could be quite easily followed. 

 Observations were made every five minutes and drawings with the 

 camera lucida about every fifteen minutes. 



At 11.15 a.m. two individuals were singled out for study which were 

 lying close together and were apparently the result of the division of 

 a single rod (Plate XII, fig. a). 



For the first 1^ hours, there was very little change beyond a slight 

 increase in the length of both rods. At 12.55 there was a slight con- 

 striction in the middle of one of them (fig. b) ; a transverse wall was 

 formed and at 1.10 p.m. the division was complete (fig. c). The second 

 rod increased to nearly three times its original length and then divided 

 in a similar way (figs./, g). After this, all the individuals under obser- 

 vation continued to divide rapidly ; about 15 minutes elapsed from the 

 first sign of constriction to the completion of division and in another 

 20 minutes the two new rods thus formed had attained their maximum 

 size and had begun to divide again. The segments were not always of 

 equal size, 



