y. 



MOULDS (Penicillium and Mucor). 



Torula, Protococcus and Amoeba are extremely simple con- 

 ditions of the two great kinds of living matter which are 

 known as Plants and Animals. No plants are simpler in 

 structure than Torula and Protococcus, and the only animals 

 which are simpler than Amoebce, are essentially Amcebce 

 devoid of a nucleus and contractile vesicle. Moreover, how- 

 ever complicated in structure one of the higher plants may 

 be in its adult state, when it commences its existence it is as 

 simple as Torula or Protococcus, or at most as Torula or Pro- 

 tococcus would be if it possessed a distinct nucleus ; and the 

 whole plant is built up by the fissive multiplication of the 

 simple cell in which it takes its origin, and by the subsequent 

 growth and metamorphosis of the cells thus produced. The 

 like is true of all the higher animals. They commence as 

 nucleated cells, essentially similar to Amoebae, and colourless 

 blood-corpuscles, and their bodies are constructed by aggre- 

 gations of metamorphosed cells, produced by division from the 

 primary cell. It has been seen that Torula and Protococcvs, 

 similar as they are in structure, are distinguished by certain 

 important physiological peculiarities ; and the more compli- 

 cated plants are divisible into two series, one produced by the 

 growth and modification of cells which have the physiological 

 peculiarities of Torula and contain no chlorophyll, while the 



