30 ELEMENTARY BIOLOGY. [V. 



sexual process developes into a rudimentary mycelium, with 

 a single sporangium wliich constitutes the first generation 

 {A). This gives rise, by the asexual development of spores in 

 its sporangium, to the second generation (B), represented by 

 as many separate Mucores as there are spores. The second 

 generation {B) may give rise sexually to zygospores and so 

 reproduce the generation {A) ; but, more usually, an indefi- 

 nite series of generations similar to {B) are produced from 

 one another asexually, before {A) returns. 



When Mucor is allowed to grow freely at the surface of a 

 saccharine liquid, it takes on no other form than that de- 

 scribed; but, if it be submerged in the same liquid, the mode 

 of development of the younger hyphas becomes changed. 

 They break up, by a process of constriction, into short 

 lengths, which separate, acquire rounded forms, and at the 

 same time multiply by budding after the manner of Torulce. 

 Coincidentally with these changes, an active fermentation is 

 excited in the fluid, so that this " Mucor- Torula," iunction- 

 ally as well as morphologically, deserves the name of 'yeast '. 



If the Mucor-Torula is filtered off from the saccharine 

 solution, washed, and left to itself in moist air, the Torulce 

 give off very short aerial hyphse, which terminate in minute 

 sporangia. In these a very small number of ordinary mucor 

 spores is developed, but, in essential structure, both the 

 sporangia and the spores resemble those of normal Mucor. 



