H. B. Hutchinson and J. Clayton 153 



in voung cultures. The second may l)t' referred to as indirect and possibly 

 generative growth in which both cell and cell contents appear to undergo 

 a definite series of changes. 



The predominating form in young cultures will generally be found to 

 consist of simple, sinuous filaments the length of which is about ten 

 times fhe diameter. C'arbol fuchsin is fairly readily and uniformly 

 taken up and shows the slightly tapering ends of the cell. With in- 

 creasing age there occur a number of cells which begin to show differenti- 

 ation of the cell structures, the terminals becoming less intensely 

 stained, while the cell contents assume the form of a densely stained 

 equatorial band (Plate I, fig. 6) or may take up the spherical form 

 (Plate II, figs. 2 and 5). The nuclear substance then presumably takes 

 up a transverse position and finally undergoes division which is accom- 

 panied by a constriction of the cell wall. During the latter phases the 

 cell itself has become appreciably thicker and less filamentous, while 

 owing to almost complete indifl'erence to the action of the stain, the 

 cell wall is perceptible as little more than a " shadow " form (Fig. 1 below). 

 After further constriction the two halves of the cell apparently become 

 detached, the resultant oval or ovoid cells each containing a plate or 

 disc of nuclear substance which remains attached to the cell wall when 

 the spherical or sporoid stage is eventually reached. Finally, the 

 sporoid — which up to this has exhibited comparatively slight staining 

 capacity — becomes evenly and intensely stained, presumably owing to 

 a dispersion of nuclear substance, and gives rise to the thread form. 

 This, therefore, must be accepted as being merely our interpretation 

 of the differences of cell form and cell contents which may be observed 

 in stained preparations of cultures of different ages. It is, of course, 

 fully recognised that heat fixation is objectionable on account of the 

 risk of distortion of nuclear figures or of chromatin substance, and that 

 all structures which take up fuchsin are not necessarily of the nature 

 of nuclear substance. It may be mentioned, however, that identical 

 appearances are to be obtained by formaldehyde-alcohol fixation and 

 the use of stains such as those of Leishman and Geimsa. ' 



In the figure on. p. 1-54 the main intermediate stages between the 

 filamentous and the sporoid forms of iS'. ci/lopJiaga are diagrammatically 

 represented, the most frequently occurring types being arranged in 

 horizontal order from left to right, while a few of many divergent 

 examples are grouped both above and below. 



Of these variations from the normal may be mentioned the tendency 

 towards the production of highly sinuous forms in liquid media, while 



