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SCIENCE PROGRESS 



rods have departed. This sinks to the bottom, and takes its 

 place along with the other empty sheaths that have preceded 

 it. If the life of Cladothrix has run its course in ferruginous 

 waters the sheath is impregnated with ferric hydroxide, and in 

 appearance is exactly similar to a dead Leptothrix thread. 

 When the rods slip out of the open sheath they are either 

 carried away as inert bodies or else are endowed with cilia and 



Fig. 7. — Cladothrix dichotoma ; A, x 1,000 ; 

 B, x 2,000 ; C, x 2,000. 



A , Shows a rod -cell which has slipped laterally out of 

 the sheath, assumed a spiral form, and developed 

 polar cilia. B, Shows an open sheath containing 

 rod-cells in process of ejection. C, A spirally 

 shaped fragment of a Cladothrix thread, which, 

 after separation, has developed a spiral form and 

 assumed polar cilia. 



effect their own locomotion. In the Cladothrix figured by 

 Fischer the cilia are placed in a bunch immediately below one 

 of the ends of the rod, but in the British species, so far as they 

 have been examined, the cilia are placed exactly at the poles. 

 The liberation of single rods is not confined to the apex ; some 

 may take a short cut through the sheath, and either slip away 

 or else develop in attachment to the parent thread. Further 

 non-motile or motile fragments may be liberated. In the latter 

 case each rod composing the fragment is possessed of one or 



