One would believe that a unique name would make searching for information easier in the genealogical realm. I am quickly discovering that is not so.  In my search for proof of the parentage of one Mehitable Arms, I am coming up empty.  I have the research of two other genealogists that list her as the daughter of Thomas Arms and Polly Coolidge.  Searching on familysearch.org  I found two possibilities for Thomas Arms.
1.
 
 
 
  | Massachusetts, Births and Christenings, 1639-1915, index,
  <i>FamilySearch</i>
  (https://familysearch.org/pal:/MM9.1.1/FZ98-DFH : accessed 27 Sep 2014),
  Thomas Arms, 03 Aug 1759; citing DEERFIELD,FRANKLIN,MASSACHUSETTS, ; FHL
  microfilm 186146. | 
 
  | Name: | 
  Thomas Arms | 
 
  | Gender: | 
  Male | 
 
  | Christening Date: | 
   | 
 
  | Christening Place: | 
   | 
 
  | Birth Date: | 
  03 Aug 1759 | 
 
  | Birthplace: | 
  DEERFIELD,FRANKLIN,MASSACHUSETTS | 
 
  | Death Date: | 
   | 
 
  | Name Note: | 
   | 
 
  | Race: | 
   | 
 
  | Father's Name: | 
  Thomas Arms | 
 
  | Father's Birthplace: | 
   | 
 
  | Father's Age: | 
   | 
 
  | Mother's Name: | 
  Lydia | 
 
  | Mother's Birthplace: | 
   | 
 
  | Mother's Age: | 
   | 
 
  | Indexing Project (Batch) Number: | 
  C50172-2 | 
 
  | System Origin: | 
  Massachusetts-ODM | 
 
  | GS Film number: | 
  186146 | 
 
  | Reference ID: | 
   | 
 
AND
2.
 
 
 
  | "Massachusetts, Births and Christenings, 1639-1915,"
  index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VQXL-XFM :
  accessed 28 Sep 2014), Thomas Arms, 22 Jun 1729; citing
  DEERFIELD,FRANKLIN,MASSACHUSETTS, ; FHL microfilm 0873741 IT 3. | 
 
  | Name: | 
  Thomas Arms | 
 
  | Gender: | 
  Male | 
 
  | Christening Date: | 
   | 
 
  | Christening Place: | 
   | 
 
  | Birth Date: | 
  22 Jun 1729 | 
 
  | Birthplace: | 
  DEERFIELD,FRANKLIN,MASSACHUSETTS | 
 
  | Death Date: | 
   | 
 
  | Name Note: | 
   | 
 
  | Race: | 
   | 
 
  | Father's Name: | 
  William Arms | 
 
  | Father's Birthplace: | 
   | 
 
  | Father's Age: | 
   | 
 
  | Mother's Name: | 
  Rebeckah | 
 
  | Mother's Birthplace: | 
   | 
 
  | Mother's Age: | 
   | 
 
  | Indexing Project (Batch) Number: | 
  C50172-1 | 
 
  | System Origin: | 
  Massachusetts-ODM | 
 
  | GS Film number: | 
  0873741 IT 3 | 
 
  | Reference ID: | 
  
  | 
 
Since I don't have any vital statistics on the Thomas Arms I am looking for, I am exploring all possibilities and then ruling out as I go.  I pasted this into an Excel spreadsheet, side by side.  That is the easiest way for me to do comparisons.  I then found the marriage records for the parents mentioned in the two results above.
1.
 
 
 
  | "Massachusetts,
  Marriages, 1695-1910," index, FamilySearch
  (https://familysearch.org/pal:/MM9.1.1/FHT2-5HS : accessed 28 Sep 2014),
  Thomas Arms and Lydia Alvord, 12 Jul 1753; citing reference Vol. 1 Pg. 304;
  FHL microfilm 186146. | 
 
   | 
   | 
 
  | Name: | 
  Thomas Arms | 
 
  | Birth
  Date: | 
   | 
 
  | Birthplace: | 
   | 
 
  | Age: | 
   | 
 
  | Spouse's Name: | 
  Lydia Alvord | 
 
  | Spouse's Birth Date: | 
   | 
 
  | Spouse's Birthplace: | 
   | 
 
  | Spouse's Age: | 
   | 
 
  | Event Date: | 
  12 Jul 1753 | 
 
  | Event Place: | 
  Sunderland, Franklin, Massachusetts | 
 
  | Father's Name: | 
   | 
 
  | Mother's Name: | 
   | 
 
  | Spouse's Father's Name: | 
   | 
 
  | Spouse's Mother's Name: | 
   | 
 
  | Race: | 
   | 
 
  | Marital Status: | 
  Unknown | 
 
  | Previous Wife's Name: | 
   | 
 
  | Spouse's Race: | 
   | 
 
  | Spouse's Marital Status: | 
  Unknown | 
 
  | Spouse's
  Previous Husband's Name: | 
 
  | Indexing Project (Batch) Number: | 
  M50052-8 | 
 
  | System Origin: | 
  Massachusetts-EASy | 
 
  | GS Film number: | 
  186146 | 
 
  | Reference ID: | 
  Vol. 1 Pg. 304 | 
 
AND
2.
 
 
 
  | "Massachusetts,
  Marriages, 1695-1910," index, FamilySearch
  (https://familysearch.org/pal:/MM9.1.1/FC4H-H97 : accessed 28 Sep 2014),
  William Arms and Rebekah Nash, 28 Oct 1720; citing reference ; FHL microfilm
  0873741 IT 3. | 
 
   | 
   | 
 
  | Name: | 
  William Arms | 
 
  | Birth Date: | 
   | 
 
  | Birthplace: | 
   | 
 
  | Age: | 
   | 
 
  | Spouse's Name: | 
  Rebekah Nash | 
 
  | Spouse's Birth Date: | 
   | 
 
  | Spouse's Birthplace: | 
   | 
 
  | Spouse's Age: | 
   | 
 
  | Event Date: | 
  28 Oct 1720 | 
 
  | Event Place: | 
  Deerfield, Franklin, Massachusetts | 
 
  | Father's Name: | 
   | 
 
  | Mother's Name: | 
   | 
 
  | Spouse's Father's Name: | 
   | 
 
  | Spouse's Mother's Name: | 
   | 
 
  | Race: | 
   | 
 
  | Marital Status: | 
  Unknown | 
 
  | Previous Wife's Name: | 
   | 
 
  | Spouse's Race: | 
   | 
 
  | Spouse's Marital Status: | 
  Unknown | 
 
  | Spouse's
  Previous Husband's Name: | 
 
  | Indexing Project (Batch) Number: | 
  M50052-8 | 
 
  | System Origin: | 
  Massachusetts-EASy | 
 
  | GS Film number: | 
  186146 | 
 
  | Reference ID: | 
  Vol. 1 Pg. 244 | 
 
 
These I also pasted into my spreadsheet next to one another.  Another check for a marriage record for Thomas Arms revealed a record of his marriage to Polly Coolidge.
 
 
 
  | Massachusetts, Marriages, 1695-1910, index,
  (https://familysearch.org/pal:/MM9.1.1/FCMJ-6WG : accessed 27 Sep 2014),  MM9.1.1/FCMJ-6WL:, Thomas Arms and Lydia
  Alvord,12 Feb 1785; citing reference ; FHL microfilm 873740. | 
 
  | Name: | 
  Thomas Arms | 
 
  | Birth Date: | 
   | 
 
  | Birthplace: | 
   | 
 
  | Age: | 
   | 
 
  | Spouse's Name: | 
   | 
 
  | Spouse's Birth Date: | 
   | 
 
  | Spouse's Birthplace: | 
   | 
 
  | Spouse's Age: | 
   | 
 
  | Event Date: | 
  12 Feb 1785 | 
 
  | Event Place: | 
  Montague, Franklin, Massachusetts | 
 
  | Father's Name: | 
  Thomas | 
 
  | Mother's Name: | 
  Polly Coolidge | 
 
  | Spouse's Father's Name: | 
   | 
 
  | Spouse's Mother's Name: | 
   | 
 
  | Race: | 
   | 
 
  | Marital Status: | 
   | 
 
  | Previous Wife's Name: | 
   | 
 
  | Spouse's Race: | 
   | 
 
  | Spouse's Marital Status: | 
   | 
 
  | Spouse's Previous Husband's Name: | 
 
  | Indexing Project (Batch)
  Number: | 
  M50178-1 | 
 
  | System Origin: | 
  Massachusetts-EASy | 
 
  | GS Film number: | 
  873740 | 
 
  | Reference ID: | 
   | 
 
 
I went to Google.com and searched for "Thomas Arms Polly Coolidge Franklin Massachusetts" and found another source for a marriage record for them.  Polly was from Coleraine, Massachusetts.
PART I 
COLRAIN MARRIAGES TO THE END OF THE YEAR 1849 
Extracted From 
Vital Records of Colrain, Massachusetts 
To the End of the Year 1849 
Salem, Mass., 1934 (no copyright statement) 
[transcribed by Dave Swerdfeger]
I tried to find a digital copy of this book without success.  I would like to know the meaning behind the abbreviations in the entry.
Many years ago I corresponded with someone regarding the Rice connections to the Hazeltons.  Paul Hazelton married Mary Rice. Mehitable Arms married Royal Harvey Hazelton. Online I found the following:
Thomas Arms married Polly Coolidge.1 Thomas Arms was baptized on 6 August 1758 at Deerfield, MA.2 He was born on 3 August 1759 at Deerfield, MA, (sic).
Child of Thomas Arms and Polly Coolidge
Mehitabel Arms+
Citations
1 [S1351] Hupfer.
2 [S1114] Thomas W. Baldwin, Deerfield, MA, Vital Records.
© Copyright 2002, 2011 by the Edmund Rice (1638) Association                                [S1114] Baldwin, Thomas W.. Vital records of Deerfield, Massachusetts, to the year 1850. Boston, MA: Wright & Potter, 1920.  
http://www.george-king.com/Planter/p5.htm#i256767
Notice the two different birthdates and the corresponding sources.  I went back to familysearch.org and found this record:
 
 
 
 
  
  
   
   
    Name: Thomas Arms 
        Gender: Male 
        Christening Date: 06 Aug 1758 
        Christening Place: DEERFIELD,FRANKLIN,MASSACHUSETTS 
        Birth Date: 03 Aug 1759 
        Birthplace:  
        Death Date:  
        Name Note:  
        Race:  
        Father's Name: Thomas Arms 
        Father's Birthplace:  
        Father's Age:  
        Mother's Name: Lydia 
        Mother's Birthplace:  
        Mother's Age:  
        Indexing Project (Batch) Number: C50172-1 
        System Origin: Massachusetts-ODM 
        GS Film number: 0873741 IT 3 
        Reference ID:  
        Citing this Record: 
        "Massachusetts, Births and Christenings, 1639-1915," index,
    <i>FamilySearch</i> (https://familysearch.org/pal:/MM9.1.1/VQXL-XF3
    : accessed 28 Sep 2014), Thomas Arms, 03 Aug 1759; citing , ; FHL microfilm
    0873741 IT 3. | 
    
 
 | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
I don't know about you, but I find it hard to believe it is possible to christen a child who has yet to be conceived.  But you can clearly see where the two cited sources on http://www.george-king.com/Planter/p5.htm#i256767 found their information.  The question remains, which year is correct. 
An additional search on Find-A-Grave I found the following:
 
 
 
  
   
   
    Birth: 
    unknown 
        Death:  Sep. 12, 1756 
        Deerfield 
        Franklin County 
        Massachusetts, USA 
        Thomas was the son of William Arms. 
        INSCRIPTION: Thomas son of Mr & Mrs William Arms died September 12,
    1756 aged ??   
        Burial: 
        Old Deerfield Burying Ground  
        Deerfield 
        Franklin County 
        Massachusetts, USA  
        Created by: Geo Clinton 
        Record added: Oct 04, 2007  
        Find A Grave Memorial# 21948755 |  
 
 | 
Thomas Arms who married Lydia Alvord had a son, Thomas Arms, in 1759 and Thomas Arms, son of William Arms and Rebekah Nash, died in 1756. My conclusion is that they are not the same person.  Below is the Find-A-Grave memorial for Thomas Arms who died in 1808.
 
 
 
  Birth:  1730 
    Death:  Aug. 17, 1808 
    On July 12, 1753, Thomas Arms married Lydia Alvord in Sunderland, Franklin
  County, MA.   
    Family links:  
     Spouse: 
      Lydia Alvord Arms (1736 - 1802)*
   
     Children: 
      Eliphaz Arms (1754 - 1826)* 
      Thomas Arms (1759 - 1832)* 
      Lucy Arms (1774 - 1836)* 
     *Calculated relationship  
    Inscription: 
    Thomas Arms 
    Died 
    Aug. 17, 1808 
    AE 78 yrs. 
     Burial: 
    Sugarloaf Street Cemetery  
    South Deerfield 
    Franklin County 
    Massachusetts, USA  
    Created by: acpflute 
    Record added: Jul 13, 2012  
    Find A Grave Memorial# 93549255 | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
I was still looking for Thomas Arms who married Polly Coolidge.  Find-A-Grave had a memorial, but I didn't believe it to be the same man.
 
 
 
 
  Birth:  Aug. 3, 1759,
  Deerfield,Franklin County, Massachusetts, USA 
    Death:  Jun. 2, 1832, Deerfield,
  Franklin County, Massachusetts, USA 
    Thomas Arms was the son of Thomas and Lydia Alvord Arms. 
    Head of family   
    Family links:  
     Parents: 
      Thomas Arms (1730 - 1808) 
      Lydia Alvord Arms (1736 - 1802)
   
     Spouse: 
      Hannah Boyden Arms (1774 - 1861)*
  Spouse #2 
     Sibling: 
      Eliphaz Arms (1754 - 1826)* 
      Thomas Arms (1759 - 1832)  
    *Calculated relationship  
    Inscription: 
    Thomas Arms 
    Died 
    June 2, 1832 
    AE 73 yrs.  
    Burial: 
    Sugarloaf Street Cemetery ,  South Deerfield, Franklin County,
  Massachusetts, USA  
    Created by: acpflute 
    Record added: Jul 13, 2012  
    Find A Grave Memorial# 93549176 | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
This is my Thomas Arms, but who is Hannah Boyden??  One of the search results took me to an Arms family genealogy website where I found this:
 
 
 
 
   
    ID: I1363 
    Name: Thomas ARMS Jr. 1 
    Sex: M 
    Birth: 3 AUG 1759 
    Death: 2 JUN 1832 
    Change Date: 18 JAN 2003 
     
    Father: Thomas ARMS b: 1729  
    Mother: Lydia ALVORD 
     
    Marriage: 1. Polly COOLIDGE b: 7 FEB 1765 in Weston, Massachusetts 
     
    Child: Mehitable ARMS b: 22 OCT 1786 in Deerfield,Franklin,Ma 
     
    Marriage: 2. Hannah BOYDEN 
    Married: OCT 1795 
     
    Sources: 
    Text: "A Genealogical Record of THE ARMS FAMILY in this Country"
  byEdward W. Arms. 1877. | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
I was able to find a digital copy of this book.https://archive.org/details/genealogicalreco00byuarms and under the heading, "Third Generation" is found this entry "9 Thomas, born 1729, married Lydia Alvord, South Deerfield" on page seven.  Then on page nine is this entry "16 Thomas Jr., born Aug 3, 1759, died June 2, 1832, married Polly Coolidge, died June 1794, married Hannah Boyden, Oct, 1795."  Finally on page 16 I find the entry for Mehitable Arms!
 
9 Children of Thomas, Jr., son of Thomas. Deerfield.
Mehitabel, born Oct. 22, 1786.
Polly, born Feb. 9, 1789.
Senv, born Oct. 22, 1791.
Dexter, born Oct. 29, 1797.
Harriet, born Sept. 3, 1799, married Aaron Dickinson.
Fidelia, born Nov. 26, 1801, married Squire Palmer, April 23, 1830.
Wealthy, born June 23, 1804, married Solomon Adkins.
John Boyden, b. June 15, 1806, m. Hannah Childs April 17, 1836.
Josiah Coolridge, born Sept. 23, 1808, married _________Bryant.
Thomas Alvord, born March 11, 1812.
Julia Alma, born Oct. 11, 1814, married Albert Clapp.
This book also says that Thomas Arms b. 1729 who married Lydia Alvord is the son of William 2nd and Rebekah Nash.  It states that William is "buried between his father and son in the old Deerfield burying ground."  The author does not cite his sources and the two Thomas Arms are buried in two different cemeteries. The book also doesn't state which son he is buried next to. 
Heartbreaking when someone's research is flawed and the author doesn't include a citation of sources.  As usual, another mystery to unravel.  I guess that's why I love genealogy!