^^ THE NEW EVOLUTION ^^ 



common origin involving unbroken continuity of life 

 from parent to child from a primitive single cell? 



Applying the knowledge that we have of the subject 

 of embryology — of the earlier stages in the develop- 

 ment of different types of animals — we may assume 

 without the possibility of successful contradiction 

 that all of the major groups of animals were formed 

 at the same time as the result of following different 

 developmental paths from the primitive single cell. 

 No other reasonable conclusion can be drawn from the 

 facts of embryology. There is no evidence of any 

 kind which would lead us to suppose that any one 

 of the major groups was derived through any of 

 the others. 



On the contrary there is strong circumstantial evi- 

 dence which indicates that none of the major groups 

 could have been derived through any of the others. 



A study of the developmental lines of animals 

 shows that developmental progress is always evi- 

 denced by increasing specialization along definite 

 structural lines at the expense of other structural 

 features. Organs may gradually become reduced and 

 perhaps disappear, but nothing is ever added. Spe- 

 cialization is always a matter of subtraction from a 

 well balanced whole. Such subtraction once started 

 may continue, or it may cease, temporarily or per- 

 manently. But a structural feature that has once 

 begun to lose importance and to dwindle never 

 reverses the developmental path; it never recovers any 

 of its lost significance. 



All of the major groups of animals differ from each 



[ill] 



