Sentence:  It was stated earlier that one purpose of this study was to extend the analysis of variability of Onset and Completion in each of the 21 <WSD>growth</WSD> centers somewhat beyond that provided by the data in Tables 1 and 2 . 
Meaning of the word marked with <WSD> tags:  (biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level