SUBORDER CAULOBACTERIINEAE 829 



fornia, 5, 1944, 253) summarize this situation as follows: "Many of the bacteria found 

 in sea water are sessile or periphytic, growing preferentially or exclusively attached 

 to solid surfaces. The sessile habit of marine bacteria is most pronounced when they 

 are growing in very dilute nutrient solutions such as sea water to which nothing has 

 been added. . . . Most sessile bacteria appear to attach themselves tenaciously to 

 solid surfaces by exuding a mucilaginous holdfast. A few have stalks. Some of the 

 sessile bacteria grow on the walls of the culture receptacle without clouding the 

 medium itself". 



The emphasis placed on the presence of a stalk by Henrici and Johnson {loc. cit.) 

 seems artificial. In fact it may be questioned whether mere attachment by a hold- 

 fast or otherwise is a character of fundamental importance from the taxonomic 

 standpoint. Henrici and Johnson's arrangement of these poorly known bacteria, 

 however, has certain practical advantages and it has therefore been retained in this 

 edition of the Manual with such modifications as seem to be clearly indicated by 

 the progress that has been made since their outline was published. 



The submerged slide technique as employed by Henrici (Jour. Bact., 25, 1933, 277) 

 and by ZoBell and Allen (Proc. Soc. Exper. Biol, and Med., 30, 1933, 1409) has proved 

 to be most useful for studying bacteria that live attached to a substrate. 



