MONEBA. 21 



and assimilative ; (4) it is metabolic and secretory in the 

 «ense that the Moner digesls and separates the portions 

 xecessary for food from those which it rejects as waste ; (5) 

 it is respiratory, the changes involved in taking food, es- 

 "pecially oxygen, causing the production of and excretion of 

 carbonic acid ; (6) it is reproductive. 



It is difficult to conceive of a simpler form of life than 

 Protammia or Protomonas. Are the Moners animals or 

 plants, or do they represent a neutral division or group of 

 Jorms ? It was formerly thouglit tliat Amoeba was the sim- 

 plest possible form of life, but we shall see that that animal 

 is an undoubted organism, possessing a permanent organ, 

 the nucleus. Moreover, the Amceba intergrades with the 

 other Ehizopods which are undoubted animals, while the 

 ■simplest Monera have no characters which absolutely sepa- 

 rate them on the one hand from the plants or on the other 

 ^rom the animals. Their relation to the plants is seen in 

 the fact that, besides the resemblance to the lowest plants, 

 the cyst of Protomonas is composed of cellulose, while the 

 granular contents of tlie body become colored with chlo- 

 Tophyll.* 



For these reasons, Ilaeckel, the discoverer of the Monera, 

 j-egards them as neutral beings, neither plants nor animals. 

 Eut by comparison with other Protozoa, we shall see that 

 the Monera only differ from the monads and Ammlm by the 

 ^absence of a nucleus. This may yet be found to occur in 

 the Monera, and from this fact we separate the group only 

 provisionally from the Rhizopoda. The Oregarince also pass 

 through a true Moner-stage. This indicates that the 

 Monera ai'e allied rather to animals than plants. Another 

 point of difference from plants is the fact that, like the 

 Amceba, they engulf living plants (desraids, etc.) and ani- 

 mals (Infusoria), the only plants known to do this being the 

 -singular Myxoviycetes, whose position is uncertain, some 

 naturalists (Allman) regarding it as an animal. 



It is probable that the Monera were the earliest beings to 



* On the other hand, cellulose occurs in the integument of Tunicates, 

 -and various parts of Articulates and Vertehrates, while chlorophyll 

 ■occurs in the Infusoria ani Hydra. 



