AM(EBJ. 141 



The inference from the one-celled germ-form to the 

 one -celled parent-form is so simple, and yet so full of sig- 

 nificance, that it is impossible to lay too much stress upon 

 it. Naturally the first question arising is, whether there 

 exist at the present day any one-celled organisms, from the 

 form of which we may draw an approximately correct 

 conclusion as to the one-celled ancestors of many-celled 

 organisms ? The answer to this question is undoubtedly 

 affirmative. There are most certainly one-celled organ- 

 isms now in existence, the whole organization of which is 

 but that of a permanent egg-cell; there are independent 

 one-celled organisms, which never undergo any further 

 development, which pass their whole lives as simple cells, 

 and as such reproduce themselves without attaining to any 

 higher development. We now know a great number of such 

 one-celled organisms, for example, the Gregarina, Flagellata r 

 Acineta, Infusoria, etc. But one among them is especially 

 interesting to us, because it affords the most complete 

 answer to our question, and must be regarded as the one- 

 celled primary organism which most nearly approaches the 

 type-form of the race. This organism is the Amoeba. 



The name Amoebae has long been applied to a number of 

 microscopic one-celled organisms, which are by no means 

 rare, and are indeed widely distributed, principally in fresh 

 water, but also in the ocean ; lately they have been found 

 inhabiting moist earth. When one of these living Amoebae 

 is placed in a drop of water under the microscope and 

 greatly magnified, it appears to be a roundish body of very 

 irregular and varying form (Fig. 13). Enclosed in the soft, 

 slimj 7 , half-fluid body, which consists of protoplasm, we can 

 only see a small solid or vesicular substance, which is the 



