thank you for your responses. It seems that Miss Horner really did not
fully comprehend this phrase, simply leaving purimaviññaanam aside (it's not
the point here to investigate why she translated this way).
I found in the PED the exact translation for the expression sangaha.m
gacchati:
to be comprised, included, or classified SnA 7, 24, 291. --
3. inclusion, i. e. constitution of consciousness, phase Miln 40.
However I still wonder what means "the previous consciousness to be
included (or comprised) in the latter consciousness". Why "inclusion"? As
far as I know, the first consciousness in this life arises in dependence on
the last consciousness in the previous life. Strange to express this
dependence as a kind of inclusion, but, anyway, the feedback you provided
helped me to clarify this question.