Greek and Sanskrit neuter plural and related questions

From: Andrew Jarrette
Message: 46382
Date: 2006-10-16

Can anyone tell me why it is that Greek neuter o-stem plurals end in
<-a> and not <-e:>, as their counterparts in Latin, Gothic, Slavic and (I think) Vedic would suggest? 
  
  Also, I have heard that some consider the Latin eh2-stem ending <-a>,
as well as the neuter o-stem plural <-a>, to represent a short vowel
derived from an Indo-European short vowel, -h2 which would correspond to
the -i- of Sanskrit <janih.> "woman" (if I remember aright here about
the Sanskrit word).  Does the consensus lean more towards *-eh2 or
towards *-h2?  And if the Latin vowel was always short, why does it remain
as <-e> in French while other short unstressed vowels were lost in
French (and Catalan, Provencal)?
  
  A further question: what is the origin of the Greek feminine plural
<-ai> (also pronominal, as <tai>)?  If it is of the same origin as Latin
<-ae>, i.e. analogical, why don't we have <-e:i> instead?
 
Just thought of two more:  1.  What is the origin of the nasal that is so pervasive in the neuter plurals of classical Sanskrit?  I take it the <-i> is from neuter consonant stems, but is the nasal that precedes (immediately or before <s>) just a default glide before the appended <-i>, extended analogically to the position before <s>?  Or is it of other origin?
2.  What is the origin of the <n> that precedes the genitive plural ending in Sanskrit (e.g. <-a:na:m)?  Is it transferred from the n-stems?  Is it a dissimilation of an earlier /m/, i.e. <-a:na:m> would be from earlier <-a:ma:m>, which might itself be the original genitive plural ending of the o-stems with an added secondary <-a:m> imported from the consonant stems?  Or is it a default glide between stem and ending?
Thanks in advance,   
Andrew