THE WONDERS OF LIFE 



that this living matter must be regarded as the real 

 vehicle of the phenomena of life. As the membrane 

 was now recdgnized to be non-essential, of secondary- 

 growth, and completely wanting in some cases, there 

 remained only two essential parts of the cell — the outer 

 soft cell body, consisting of protoplasm, and the inner 

 firm nucleus, consisting of a similar substance called 

 nuclein. The original naked cell was now like a cherry 

 or plum without the skin. This new idea of the cell, 

 formulated forty years ago, which I endeavored to con- 

 firm in my monograph on the radiolaria (1862), is now 

 generally accepted, and the cell is defined as a granule 

 or particle of protoplasm (= cytoplasm) enclosing a firm 

 and definite nucleus (or caryon , consisting of caryoplasm) . 

 This would be a good occasion to glance at the errors 

 to which microscopic investigation and the conclusions 

 based on it are liable. Although KoUiker in 1845, 3-"^ 

 Remak in 1851, had drawn attention to the existence of 

 naked cells, and had compared their movements (for 

 instance, in lymph-cells) to those of the protoplasm in 

 plant-cells, the majority of the leading microscopists 

 clung for twenty years to the dogma that every cell 

 must have a membrane ; the definite outline which even 

 a naked cell must show in a different refracting medium 

 was taken to be the sign of a special and anatomically 

 separable membrane. It would be just as correct to 

 talk of a protective membrane on a homogeneous glass 

 ball; its outline is sharply defined. In the long contro- 

 versy that "exact" observers sustained as to the pres- 

 ence or absence of a membrane, this optical error — the 

 false interpretation of a sharp contour — counted for a 

 good deal. It is much the same with other conflicts of 

 ' ' exact ' ' observers who give their ' ' certain observations ' ' 

 as facts, whereas they are really inferences from imper- 

 fect observations on which different interpretations may 

 be put. 



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