AND CONTENTS OF THE MOUTH. 427 



the stem, like the hairs of a bottle brush. They are not, besides, 

 methodically arranged, but stretch out very much, like stems des- 

 tined to vegetate on their own account, rather than to complete 

 the organism bearing them. The filaments of Leptothrix parasitica 

 implant themselves also upon the stem of Zygnema, a, a, or of 

 Cladot/irix, b, b, which feeds them, by means of bulbs, or spores 

 originated in them, s, s, as the Fig. 22 shows still better (same 

 staining, magnified to 1,600 diameters) : spores which are not 

 seen at all at the insertion of our points. And still less the fila- 

 ments of Leptothrix parasitica are seen to drop at last from the 

 central stem, and swim in the medium with the same briskness of 

 our spindle-like, comma, or serpentine bacilli. 



Various Aspects and Forms. 



In the preceding Memoir we have spoken of various forms and 

 appurtenances of the parasite in question ; we specially point out 

 the bifurcations and trifurcations towards the seat of certain fila- 

 ments, with tiny radical swellings, like haustoria; and then the 

 more pronounced ones, some at the knots, some at the apex : the 

 latter like small heads. We have already mentioned the other 

 apical swellings (fertile filaments), club-shaped. 



We now go on to describe a third form of apical expansions, 

 very scarce, which, provisionally, we shall denominate sheath 

 expansion. 



Such an expansion, represented in Fig. 28 (stained with gentian 

 violet, magnified to 3,100 diameters), is very pale, has streaks in 

 its contour, not detected with inferior objectives. Its paleness 

 cannot be attributed to insufficient colouring, because the examined 

 form rose on the top of a filament (likewise pale) in the midst of a 

 thick and very pretty tuft of ears brilliantly stained (of the 

 kind shown at Fig. 12), and nearly surpassed them with its 

 point. The external contour is very slender from the base of the 

 expansion up to its point, and between the internal stem and the 

 exterior contour are seen numerous slender, tiny, transverse 

 threads, which are attached to the external sheath by means of 

 more prominent small dots. 



At first we could not understand the probable meaning of this 

 structure. That it was not to be taken for the club-like expansions 



