THE BLASTOMYCETES 161 



particularly in evidence. They are sometimes considered 

 diagnostic of pollution with animal matter, but this is 

 not invariably true. The growth may be white, grey, 

 pink, red, or violet. The filaments contain sulphur 

 particles, seen as highly refracting granules (see p. 6). 

 They can decompose sodium sulphate in suitable organic 

 solutions. 



Crenothrix Kuhniana. 



This is found in water containing organic matter or 

 iron. It sometimes occurs in such great numbers that 

 the water is unusable owing to the unpleasant odour 

 and taste it produces. The organism produces a thick 

 vegetable mass in the water, either brown or greenish 

 in colour, frequently imparting a reddish or greenish tint 

 to the water (see p. 6). 



CHAPTER XV 

 THE BLASTOMYCETES 



Blastomycetes, or yeasts, are round or oval unicellular 

 organisms, consisting of granular ' cytoplasm ' (hyaline 

 in healthy, granular in old cells), surrounded by a wall 

 of cellulose. One or more colourless lacunae (vacuoles) 

 are sometimes seen, particularly in healthy cells. A 

 nucleus (or what is taken for one) may sometimes be 

 seen. The salient character of this group is the method 

 of reproduction by budding (gemmation) : a bud is 

 extruded from the parent cell, and, after enlarging, 

 separates. Torulce seem to be restricted to this method 

 of multiplication, but Saccharomycetes can, in addition, 

 reproduce by spore formation. Minute spherical bodies 

 occur within the vacuoles in active movement, but their 

 function is not known. In the absence of ample suit- 

 able nourishment, the contents of the cells become homo- 

 geneous, and then two, four, or, in the case of Schizo- 

 saccharomyces octosporus, eight, shining spots are seen, 

 surrounded with a thick membrane. In the course of 

 time these new cells (ascospores) become liberated by 

 dissolution of the mother cell. On introducing these 

 spores, which are 4 IJL to 5 JLI in diameter, into a saccharine 



11 



