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THE AMERICAN NATURALIST [Vol. L 



tinned existence is the complex body or cell-common- 

 wealth of which they form an integral part. Bnt in the 

 simplest forms of life the whole body of the living indi- 

 vidual may reach no higher degree of complexity than 

 the single cell, which is then seen as an organism physio- 

 logically complete in every respect, living a free and in- 

 dependent life in Nature and competing with other or- 

 ganisms of all kinds, simple or complex, in the universal 

 struggle for existence amongst living beings. This state- 

 ment of the "cell-theory" is that with which, I believe, the 

 majority of modern biologists would agree ; not without, 

 however, some dissentients, amongst whom I personally 

 am not to be numbered. 3 



The fundamental importance of the cell as a complete 

 living organism, whether maintaining itself singly and in- 

 dependently or in union with other similar but individually 

 specialized units, has made it the object of intensive and 

 concentrated study, not only by those who group them- 

 selves according to their special points of view as zoolo- 

 gists, botanists, physiologists, etc., but also by a class of 

 investigators who take the cell itself as the subject of a 

 branch of biological investigation termed cytology, which 

 deals with cells in a general manner independently of 

 their provenance, whether animal or vegetable. Some 

 knowledge of the cell and its activities is necessary at the 

 present time for every one concerned with the study of 

 living things, whether that study is pursued for its own 

 sake and with disinterested objects, or with the intention 

 of applying scientific principles to practical aims, as in 

 medicine or agriculture. One might have expected, there- 

 fore, that at least some elementary understanding of the 

 nature and significance of the cell, and the importance of 

 cellular activities in the study of life and living things, 

 would have formed at the present time an indispensable 

 part of the stock of knowledge acquired by all intelligent 

 persons who are ranked as "educated" in popular esti- 



These experiments afford strong support to the view that the cell is to be 

 regarded primarily as an independent living organism. 



