V. 



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 ani- 

 mals which are simpler than Amo>bcz, are essentially Amoeba. 

 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 subse- 

 quent 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 colour- 

 less blood-corpuscles, and their bodies are constructed by 

 aggregations of metamorphosed cells, produced by division 

 from the primary cell. It has been seen that Torula 

 and Protococcus, similar as they are in structure, are dis- 

 tinguished by certain important physiological peculiarities ; 

 and the more complicated 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 other, and far larger, series 



