SYSTEMATIC AND DESCRIPTIVE. 3^7 



sorption in the yellow, and a weaker band in the 

 green and blue, as well as a darkening in the more 

 refrangible half of the spectrum. In the cocci, 

 especially of the older vesicles, dark granules are 

 to be seen, which consist of sulphur. The micro- 

 organisms occur on the surface of marshes, or on 

 water in which algae are rotting. They form a 

 rose-red, blood-red, violet-red, or violet- brown 

 scum ; and sometimes in such quantity that whole 

 marshes and ponds may be coloured blood-red by 

 them. 



All the following hitherto described as distinct species, 

 are probably only phase-forms of Beggiatoa roseo-per- 

 sicina. 



Spirillum sanguineum, Cohn (Ophidomonas 

 san guinea). Threads 3 JJL and more in thickness with 

 2 2\ spirals, each 9 12 /z- high, with their ends provided 

 with rlagella. Their colour is due to the presence of red- 

 dish granules contained in the cells. They were observed 

 in brackish water with putrefying substances. 



Spirillum rosaceum, Klein Resembles Spirillum 



undula, but is reddish in colour ; the colouring matter is 

 insoluble in water, alcohol, or chloroform. 



Spirillum violaceum, Warming. Threads, cres- 

 cent-shaped, or possessing i-J- or I spiral, with their ends 

 broad, rounded, and provided with flagella. The colour is 

 due to the contents, which are violet. 



Monas vinosa. Round or oval cells of about 2*5 ^ 

 in diameter, often united in pairs. Their motion is slow 

 and tremulous, and the cell substance pale-red, with dark 

 grains interspersed. Flagella have not been observed. They 

 were observed in water with decaying vegetable matter. 



