6 ORGANIC DEPENDENCE AND DISEASE 



the existence and earliest appearances among these ele- 

 mentary expressions of life, of conditions which show an 

 actual mutual dependence of creatures one upon another; 

 that is to say, of the conditions commonly known variously 

 as symbiosis, mutualism and parasitism. Such evidences 

 are not easy to acquire among primitive forms of life as 

 preserved in the rocks of the earth's historic record, but 

 persistent and long-continued search with the aid of a va- 

 riety of special procedures adapted to the extraction of the 

 peculiar character of the material employed, enlarged by 

 the inspection of many great museum collections and joined 

 with the help of generous colleagues and the special sup- 

 port of the National Academy of Sciences, has resulted in 

 even so much light on these significant paleopathologic 

 problems as is here set forth. 



The writer desires to present his facts without embar- 

 rassing detail and his conclusions without bias. In his own 

 justification for both he may urge a long acquaintance with 

 nature's modes in the preservation of such materials in the 

 fossil state and reasonable familiarity, based upon com- 

 parative morphology, with the forms of life that go to make 

 up the earlier faunas and floras of the earth. 



It will be observed, and special emphasis is put on this, 

 that these chapters deal with the lower forms of life, the 

 invertebrates among animals and cryptogams among the 

 plants. The actual outstanding evidences of pathological 

 and traumatic lesions among extinct animals of the verte- 

 brate type are not comprehended within this discussion as 

 such phenomena are registered only among faunas of the 

 earth too late and too specialized for our consideration. 

 Such lesions have been noted by several students of verte- 

 brate paleontology and most interestingly brought together 

 by Dr. Roy L. Moodie, whose investigations into the history 

 of such registered conditions and of the possible effect of 

 disease in the extermination of races of the higher animals 

 through the later ages of the earth are very suggestive to 



