548 MANUAL OF ELEMENTARY ZOOLOGY 



no means certain. The organised body is one thing. The 

 life in it is quite another. On this point cases of suspended 

 vitality (p. 117) are an interesting commentary. 



Organised bodies are characterised by peculiarities of 



structure, of composition, and of origin. 

 The origin of Their peculiarities of structure and composi- 

 Bodies. tion we have already studied. We may now 



consider their origin. Here we are met at 

 the outset by a difficulty. We are bound to believe that 

 these complex structures have arisen from matter in its 

 simpler unorganised form. 1 The theories of special creation 

 and of evolution agree in regarding the unorganised world 

 as primary and organised bodies as derived from it. Yet 

 organised bodies, alive or lifeless, never, in the present 

 state of nature, arise from unorganised matter. Every such 

 body arises by the process of fission from a previously 

 existing living body. In the case of the higher organisms 

 this is no more than a truism. We know that every 

 individual of the familiar kinds of animals and plants 

 had a parent from whose body it has arisen. But there 

 are cases in which parentage is not so obvious. If the 

 dead body of any organism be heated strongly, so as to 

 kill any living things that may be in it, and placed in 

 an apparently clean vessel, closed so as to prevent the 

 entry of living organisms, it will nevertheless putrefy, 

 and microscopical examination will show that putrefac- 

 tion is accompanied by the appearance of innumerable 

 minute "micro-organisms" of various kinds (pp. 122, 

 536), some of which are indeed the cause of the putre- 

 faction. Have not these been developed from the sub- 

 stance of the dead organism without the intervention 

 of life? The answer to this question has not been 

 easily reached. One of the hardest-fought controversies 

 in the history of science has been between the supporters 

 on the one hand of the theory of Abiogenesis or Spon- 



1 It is true that the difficulty of conceiving how such a transition can 

 have taken place has led certain authorities to the theory that life is 

 coeval with matter, living substance being transferred through space 

 from one celestial body to another — almost literally as a deus ex 

 machina. Most biologists, however, are not content to give up the 

 problem in this manner, though some are willing to admit that the 

 earth may not have been the seat of the origin of life. 



