1912.] The Life-history of Cladothrix dichotoma ( Cohn). 347 



auf, welche sich durch besonders hormogonienbildenden Algen vergleichen 

 lassen. Dieselben bezeichneten sich durch besonders dicke Scbeiden und 

 eine auffallende Gruppirung ihrer Stabchen aus. Oft ebenso lang wie breit, 

 lagen die letzteren beispielsweise in weniggliederigen Eeihen zusanimen, 

 welche durch Pfropfen einer structurlosen Masse, wohl Eeste abgestorbener 

 Stabchen, getrennt waren." 



If this figure be compared with fig. 10 of this publication, in which two of 

 these broad transverse bands are shown, it will be seen that the mapping out 

 of the " hormogonia " was probably due in his cultures, and certainly in mine, 

 to the formation of very broad transverse bands of the same material as the 

 sheath. But, under appropriate treatment, these transverse bands can be 

 found between each cell. In fig. 10 we see two of these broad bands, viz., at 

 a and at b. They are obviously formed by the accumulation of sheath 

 material in those spaces left empty by the slipping out of one of the cells 

 through the sides of the sheath. The space occupied by this cell then 

 becomes filled with the same material as that composing the sheath, and so 

 the appearance presented in fig. 10 at a and at h is gradually formed. When 

 the length of such a band is equal to that of one of the cells, it often has a 

 hollow consistency, the hollow space being obviously that previously occupied 

 by a cell. In old sheaths there is no trace of the transverse bars. This may 

 be explained as follows: it is obvious that the sheath, at first soft, later 

 hardens. The growth of the contained cells however continues, with the 

 result that the apex of the sheath is burst through and the sheath, now hard, 

 remains permanently open. Whilst the sheath is hardening, however, the 

 pressure of the growing cells causes the latter to break through the transverse 

 bars, and as they closely fit the sheath the movements of the growing and 

 dividing cells would soon smooth down all projections caused by the remains 

 of the bars ; this would take place whilst the sheath was hardening and, of 

 course, after hardening no more transverse walls would be formed. It is 

 interesting to note that a similar secretion of mucilage, followed by a similar 

 hardening of this material, resulting in its complete separation from the cells has 

 been described by Hansen for yeast-cells (see Klockers, ' Garungsorganismen,' 

 p. 174). In such cases the yeast-cells are enclosed inside the meshes of a 

 hardened reticulate mucilaginous network. This hard network is obviously 

 the same kind of material as that forming the sheath of the Cladothrix cells. 



The Vegetative Cells. — The cells are usually 3-5 times as long as they are 

 broad, though they are shorter in growing cells (figs. 1, 2, 4, 10). The 

 average width is about 1^ p. By the use of stains, the cell is seen to be 

 bounded by a sharply defined double contoured membrane. The best stain 

 for the purpose is iodine. The membrane is coloured a deep brownish red, 



VOL. LXXXV. — B. 2 B 



