AND CONTENTS OF THE MOUTH. 431 



various phases of that cycle do not differ from ours, excepting in 

 what affects the production of bacteria included in filaments, 

 which Billet considers are real endogenous spores ; and we cannot 

 positively deny that such is the case in the four species studied by 

 him ; whilst in our parasite they ought, in our opinion, to be held 

 as simple gemmules of reserve. 



But from the exposition of the facts in our previous Memoir, 

 and confirmed in the present one, it clearly results that the evolu- 

 tionary cycle, so nicely delineated by Billet, cannot include all the 

 morphological phases of our Leptothrix racemosa, but only some of 

 them. In this parasite, besides that first cycle which we call 

 inferior, there is another — the superior, which comprises the 

 organs of genuine reproduction and fructification. Finally, toge- 

 ther with these two normal evolutionary cycles, there is another 

 one — accidental, called virulent, in which (according to laboratory 

 experiments) it seems that certain elements, derived from the 

 parasite itself, may, as Pommay says, develop themselves in the 

 sense of virulence. 



The first two cycles would, therefore, constitute the morpholo- 

 gical series, and the third, or virulent, cycle would, in modern 

 language, constitute the biological se?'ies of our parasite. 



Morphological Series. — Inferior Cycle. — The inferior cycle 

 embraces the following phases : — 



I. — Phase of Vegetatio?i. — The characters of this phase are 

 those assigned by Billet to the filamentous state, only that he con- 

 siders the intertwined state {etat e7ichevetre) as a distinct and later 

 phase ; whilst we believe that it, in our parasite, accompanies the 

 filamentous state, in the same manner as the mycelium or creeping 

 vegetation in fungi. In other words, the intertwined state is even 

 posterior to the isolated filaments which lead a wandering life in the 

 liquid substrata, being unable to attain a more vigorous and stable 

 one ; but it does not constitute a distinct phase, as it is quite natural 

 that, when the passage to the superior phases is precluded (aerial 

 vegetation) for want of a fit soil, the filaments intertwine and drop 

 to the bottom, without being able to spread like the mycelium of 

 fungi. However, under favourable conditions, a kind of mycelium 

 (a more complete phase of the entangled state) may be formed, 

 giving birth to an aerial vegetation, as may be specially observed 



