VARIATION STEPS 197 



of the umbella, LUDWIG), in Primula and Myosotis (number 

 of petEils ?, § 131) and very probably in certain properties of 

 Mollusca and other animals. Etc. 



Examples of mechanical concordance, embryological parallel- 

 ism and parallel variation steps are innumerable. It is by dis- 

 cerning and measuring the primordia — in the adult state and 

 in the course of the individual development — that it may 

 become possible to classify the facts and to establish their 

 biological significance. 



In this subject, as in many others, DARWIN has been the 

 pioneer. If, however, we go on talking continually and indis- 

 criminately about analogous or parallel variation, reversion, 

 ancestral characteristics, convergent adaptation (see § 65, p. 81), 

 etc., further progress will be rather slow. 



