Sentence:  For four of the six ( the anaconda and the amethystine python cannot be included for lack of data ) there is also a correlation between size at maturity and maximum length , the boa constrictor being the smallest and the Indian python the next in size at the <WSD>former</WSD> stage . 
Meaning of the word marked with <WSD> tags:  referring to the first of two things or persons mentioned (or the earlier one or ones of several); I prefer the former version to the latter one"