354 ANIMAL AGGREGATIONS 



come more clear if presented in the simplest possible form. In order 

 to free our minds of the perplexities brought in by the special re- 

 quirements of our present-day species, with their long history of 

 past adjustments to environments, or of mutational changes, let us 

 try to consider conditions existing when living molecules first 

 evolved from their non-living antecedents. 



However, whenever, and wherever life first appeared on this 

 planet, considerations which we have given in detail in the preceding 

 chapters make it highly probable that, unless the first living mole- 

 cules appeared in considerable numbers approximately simultane- 

 ously within a limited microhabitat, there would have been little 

 chance of survival; a single isolated living particle, must have suc- 

 cumbed to the unconditioned unfavorable environment. If this 

 occurred, a certain slight modification of the environment would 

 result as the particle disintegrated. In doing so, it might free some 

 X-substance, such as various workers, from Semper down to Robert- 

 son, Drzewina and Bohn, and Burnet, have assumed to be necessary 

 for the well-being of living organisms; or the decomposing proto- 

 plasmic molecule might fix, by adsorption or otherwise, some of the 

 elements of the environment harmful for a living system. In other 

 words, the living protoplasm itself or the products of its metabolism 

 during fife, or freed by death and disintegration, would probably 

 condition the immediate environment in such a manner that if an- 

 other particle of living matter appeared soon in that niche it would 

 have a better chance of survival. 



If, on the other hand, several of these living molecules appeared 

 approximately simultaneously in the same restricted microhabitat, 

 then by the processes of metabolism they would tend to condition 

 their environment similarly, and by fixation of toxic substances, 

 or by some one of the other communal activities, such as the produc- 

 tion of an X-substance, or the modification of the electrical condi- 

 tions, this primitive aggregation of living particles would show the 

 survival value which we have demonstrated is frequently exhibited 

 by present-day animal aggregations of approximately the same in- 

 tegration level. 



It may be that numerous transitions from the non-living to the 



