THE LEUCO-THIOBACTERIA 107 



either the base or the apex. The thread readily breaks up 

 into more or less equal segments which for a time are held 

 together by connecting bands of slime. The whole surface 

 of the cells is covered by a layer of slime which subsequently 

 hardens, and forms round the cells an enveloping hollow 

 tubular sheath. With further growth the apex of the line of 

 cells inside the tubular sheath is pushed out. Then each cell 

 as it wins clear of the top of the sheath becomes separated and 

 moves away. There is thus a steady emergence of cells from 

 the sheath, pushed from behind by the pressure of growth. 

 In some cases the liberated cells develop motility and swim 

 slowly away. The name rod-gonidlwn is usually given to a 

 cell of this kind. After swimming for a short time it comes 

 to rest on some object and forms a new thread (Fig. 9). 



Note on the Terms "Conidium" and " Rod-Gonidium." 

 The use of these terms is incorrect in the sense in which they are 

 employed above, as it implies that they are special organs of asexual re- 

 production. The method of reproduction in Thiothvix is one of simple 

 fission, but it is complicated by the circumstance of the fission taking 

 place inside a sheath of slime. In essentials it consists merely in fragments 

 of a thread being successively detached from the apex. 



Thiothrix nivea (Rabenhorst), Winogradsky, 1888. 



Literature. — Pollini, 1817; Oerstedt (2), 1844; Kiitzing (2), 

 1843; Rabenhorst (2), 1865; Corsini, 1905; Swellen- 

 grebel, 1909; Keil, 1912; Bavendamm, 1924. 



Synonyms. — Conferva alba (Pollini) ; Leptomitus (x^Vgardh) ; 

 Leucothrix Mucor (Oerstedt) ; Hygrocrocis nivea 

 (Kiitzing) ; Beggiatoa nivea (Rabenhorst) ; Thiothrix 

 tenuis and Thiothrix tenuissima (Winogradsky, 

 Migula, Buchanan, and Bavendamm). 



Description. — Bavendamm suggests that this species was 

 described as far back as 1817 by Pollini under the name Con- 

 ferva alba, and at various times, as is shown by the literature 

 quoted, attention has been called to it by various investigators. 

 Rabenhorst in 1865 gave to it the name Beggiatoa nivea, which 

 w^as subsequently (1S89) changed by Winogradsky to Thiothrix 



