1912.] The Life-history of Cladothrix dichotoma (Cohn). 



353 



observations on this point were chiefly of a confirmatory nature. In all 

 media growth commences by the formation in the liquid of characteristic 

 grey, easily visible flecks. Microscopically examined, each fleck is seen as 

 represented in fig. 19. This is, I think, the first time that a figure of a 

 Cladothrix colony has been published. The presence of a large number of 

 flecks gives the liquid a very turbid appearance. They usually congregate 

 at the top> but fall to the bottom when gently shaken, and remain there. 

 After a few days a flocculent grey deposit is formed. The organism is 

 strongly aerobic, and gradually liquefies gelatine when grown in gelatine 

 nutrient media. 



Motility and Organs of Movement. — Hitherto, investigations of the organs 

 of movement of Cladothrix have been confined to the cilia of single inde<- 

 pendent cells. The disposition of cilia in motile threads consisting of more 

 than one cell has not been touched upon. Motile threads of Cladothrix are, 

 however, common, and if motile single cells develop into motile threads 

 consisting of many cells, it is obvious that a development of fresh cilia 

 must also take place in order to secure an adequate propelling force. Cilia 

 preparations were first made of single motile cells. The cilia of such cells 

 have been investigated by Hoeflich (12) and by A. Fischer (6). They were 

 shown to be situated in a sub-polar position. Unfortunately, I could not 

 obtain cells in a swarming condition inside the sheath, but I was able to 

 obtain cilia preparations of several immediately after their liberation from 

 the sheath. 



In all such preparations the cilia were disposed in the polar and not in a 

 sub-polar position (figs. 26, 27). With regard to the cilia of motile threads, 

 in these also the cilia were placed at the poles of the individual cells. The 

 cilia of a thread of seven cells are shown in fig. 28, of five cells in fig. 20, 

 and of two cells in fig. 27. As the threads become longer the movement 

 gets slower ; threads of \ mm. in length move with a very slow stately 

 movement. Beyond this length movement ceases, evidently because the 

 development of cilia has not been able to keep pace with the increase of 

 mass caused by the growth and development of the cells. 



The motility and organs of movement of the liberated motile spiral threads 

 have already been described. 



The Organ of Attachment of Attached Threads. — No indication was seen of 

 a special organ of attachment. Biisgen mentions the existence of a small 

 adhesive disc, but in my cultures when attached threads were liberated there 

 was nothing to show which end had been previously attached. 



The Phylogenetic Position of Cladothrix dichotoma. — The organism that is 

 undoubtedly most closely allied to Cladothrix is Sphcerotilus natans. The 



