MODELS OF LIVING ORGANISMS 



91 



assume according to the method of their preparation. These 

 experiments can. however, hardly be regarded as ' plasmo- 

 geny ' — a means of obtaining living organisms artificially. 

 Herrera, however, took just this view in 1942 when he 

 published his New theory of the origin and nature of life.^* 



Fig. 8. Herrera's artificial cells. 



He based it on his experiments on the structures made out 

 of thiocyanates. Such structures can certainly arise, as 

 Herrera asserts, under natural conditions, but it is doubtful 

 w^hether any contemporary biologist would admit that these 

 structures are endowed with life. These structures have no 

 organised metabolism and cannot reproduce themselves. The 

 single fact of their resemblance to the structures seen in fixed 

 tissues cannot alone serve as a criterion of life. 



