194 THE KIDDLE OF THE UNIVEESE. 



cells in thousands are mortal beings, and at their 

 death their personal psychic activity is extinguished 

 like every other physiological function. 



A number of eminent zoologists — Weismann being 

 particularly prominent — have recently defended the 

 opinion that only the lowest unicellular organisms, 

 the protista, are immortal, in contradistinction to the 

 multicellular plants and animals, whose bodies are 

 formed of tissues. This curious theory is especially 

 based on the fact that most of the protista multiply 

 without sexual means, by division or the formation of 

 spores. In such processes the whole body of the 

 unicellular organism breaks up into two or more 

 equal parts (daughter-cells), and each of these portions 

 completes itself by further growth until it has the 

 size and form of the mother-cell. However, by the 

 very process of division the individuality of the 

 unicellular creature has been destroyed ; both its 

 physiological and its morphological unity have gone. 

 The view of Weismann is logically inconsistent with 

 the very notion of individual — an "indivisible" 

 entity ; for it implies a unity which cannot be divided 

 without destroying its nature. In this sense the 

 unicellular protophyta and protozoa are throughout 

 life physiological individuals, just as much as the 

 multicellular tissue-plants and animals. A sexual 

 propagation by simple division is found in many of 

 the multicellular species (for instance, in many 

 cnidaria, corals, medusae, etc.) ; the mother-animal, the 

 division of which gives birth to the two daughter- 

 animals, ceases to exist with the segmentation. 

 " The protozoa," says Weismann, " have no indi- 

 viduals and no generations in the metazoic sense." 

 I must entirely dissent from his thesis. As I was 



