XIII. 

 MOULDS (Penicillium, Etirotiicm 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, except perhaps 

 the Bacteria, are simpler in structure than Torula and Pro- 

 tocoaus, and the only animals which are simpler than Am&b<z, 

 are essentially Amcebce devoid of a nucleus and contractile 

 vesicle. Moreover, however complicated in structure one 

 of the higher plants may be in its adult state, when it com- 

 mences its existence it is as simple as Torula or Protococcus; 

 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. We have already seen that the like is true of all 

 the higher animals. They commence as nucleated cells, 

 essentially similar to Amcebce and colourless blood-corpuscles, 

 and their bodies are constructed by aggregations of meta- 

 morphosed cells, produced by division from the primary 

 cell. It has been seen that Torula and Protococcus, similar 

 as they are in structure, are distinguished by certain im- 

 portant 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 physio- 

 logical peculiarities of Torula and contain no chlorophyll, 

 while the other, and far larger, series contains chlorophyll, 



