CHAPTER III 



THE SIMPLEST FORMS OF LIFE 



THE simplest conceivable living being is a mass of 

 nndifferentiated protoplasm, and it was claimed by 

 Haeckel and others that such simple forms of life 

 do actually exist. Haeckel described under the name 

 Monera a considerable number of organisms to 

 which he attributed this simple structure ; but the 

 great improvements made of late years in microscopic 

 technique have shown that these are really much less 

 simple than was supposed. A nucleus can in most 

 cases be demonstrated, as well as other evidences of 

 differentiation. 



There are, however, a good many organisms of such 

 simple structure that we cannot positively assert that 

 they belong to either the animal or vegetable kingdoms. 

 There are in particular two groups of these indifferent 

 organisms, those included by Haeckel in his Monera, 

 such as Yampyrella and Protomyxa, and those curi- 

 ous organisms the " Slime-moulds," - Myxomycetes or 

 Mycetozoa. These two groups, which are generally 

 considered respectively as the lowest of the animal and 

 plant series, have a good many characters in common. 

 They are all, in their vegetative condition, naked masses 

 of soft, slimy protoplasm " plasmodia," which show 



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