Problems and Concepts of Evolution 9 



problems of the phylum. 



Eegardless of hypotheses of the causes of the conditions found in nature, two 

 striking facts are shown in all of the different phyla that are known, namely, 

 the fixity of a type of organization that is constant throughout the phylum, and 

 the fact that there occur changes in the different minor features of the phylum, 

 which are responsible for the production of the diversity of specific kinds of 

 living bodies, past and present. Present historical information gives little 

 satisfaction as to the origin of these huge lines of organic form that persist 

 through the history of the planet for inconceivable periods of time, and while 

 interesting hypothetical pictures of the relations and origin of these may be 

 formed, perhaps with some degree of certainty, the fact remains that there is no 

 actual information as to the method or point of origin of any of these major 

 groups of living substance. 



Within any of these lines — phyla — the information increases in amount and 

 certainty as our point of observation approaches the present, and in the living 

 things of to-day we see, and in experiment produce, changes in the characteristics 

 of some of the members of different phyla. Methods of transmutation of the 

 qualities, attributes, and conditions of the phyla are thus either proven in experi- 

 ment or with different degrees of certainty tied to operations in nature, and the 

 whole is then used in the effort to project present experiences into the past to 

 interpret and explain the production of diversity, or the evolution within the 

 phylum through its history as paleontology reveals it to us. 



In each of these histories of the phyla, and collectively true of them all, is the 

 fact that their history, as revealed in their remains, shows through time a 

 sequence of modifications, at the start simple organizations, little differentiated 

 from the phyletic type, with subsequent changes resulting in the later members 

 in complicated or specialized arrangements of the originally simple phyletic 

 characters. More rarely in restricted groups, or especially in some portions of 

 the phylum where it is possible to observe in some detail the history of a large 

 group, the history is one of progressive increase in complexity to a maximum of 

 diversity of species and structures, followed by an old-age simplification of the 

 structures and decrease of the number of different types, ending perhaps in 

 final extinction of the series, in which the last members approach in simplified 

 form somewhat the conditions of the series in its younger stages. 



There can be no doubt that precise experiment is the only method of obtain- 

 ing exact information as to the methods and factors in evolution ; nevertheless, 

 it must not, in the enthusiasm of the moment, be lost sight of that the formula- 

 tion of hypotheses of evolution from these experimental results must keep in 

 mind these undeniable facts of the history of any and all lines of living sub- 

 stance. No doubt it will be a long time before experimental efforts will be able 

 to proceed far in the elucidation of this question, but a start has been made, and 

 promises to replace, with certain knowledge of the relations of cause and effect 

 in transmutation, the plausibilities of the past, and thus enable us to undertake 

 more certainly the interpretation of the causes of the production of the forms 

 and history of the inhabitants of the planet in the past. 



Concerning the origin of the phyla and the fixity of type within each at the 



present time, and the production thereof, there is little but opinion or belief as 



to the origin and causes. These must be accepted as found, their remote history 



and origin credited to our ignorance and not to ineffective mentality or methods 



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