64 THE DATA OF BIOLOGY. 



since in the absence of preceding organic matter there was 

 no other source. The general law of evolution as well as the 

 observed actions of Protozoa and Protophyta, suggest that 

 these primordial types simultaneously displayed animal-life 

 and plant-life. For whereas the developed animal-type 

 cannot form from its inorganic surroundings either nitro- 

 genous compounds or carbo-hydrates; and whereas the de- 

 veloped plant-type, able to form carbo-hydrates from its in- 

 organic surroundings, depends for the formation of its pro- 

 toplasm mainly, although indirectly, on the nitrogenous 

 compounds derived from preceding organisms, as do also most 

 of the plants devoid of chlorophyll — ^the fungi ; we are obliged 

 to assume that in the beginning, along with the expending 

 activities characterizing the animal-type, there went the ac- 

 cumulating activities characterizing both of the vegetal types 

  — forms of activity by-and-by differentiated. 



Though the successive steps in the artificial formation of 

 organic compounds have now gone so far that substances 

 simulating proteids, if not identical with them, have been 

 produced, yet we have no clue to the conditions under which 

 proteids arose; and still less have we a clue to the conditions 

 under which inert proteids became so combined as to form 

 active protoplasm. The essential fact to be recognized is 

 that living matter, originated as we must assume during a 

 long stage of progressive cooling in which the infinitely varied 

 parts of the Earth's surface were slowly passing through ap- 

 propriate physical conditions, possessed from the outset the 

 power of assimilating to itself the materials from which 

 more living matter was formed; and that since then all liv- 

 ing matter has arisen from its self-increasing action. But 

 now, leaving speculation concerning these anabolic changes 

 as they commenced in the remote past, let us contemplate 

 them as they are carried on now — first directing our atten- 

 tion to those presented in the vegetal world. 



§ 23c. The decomposition of carbon-dioxide (§ 13) — the 



