With the Judah Thacher example, each town clerk at that particular time hand-wrote each entry. Volumes 3,4 and 7 are on microfilm 945511 while volume 18 dealing with individuals grouped in family units is on microfilm 945513. For Judah, he is listed with his siblings under John Thacher and Lydia Gorham (my ancestress). Both of these films are on permanent loan at the OGS library in Bellville, Ohio. These microfilms are the actual basis of the transcriptions of the records done by the late Robert and Ruth Sherman in two volumes (Vital Records of Yarmouth, Massachusetts to the Year 1850) also found at the OGS library. The important point to remember is the microfilm records are the original registers and are primary source evidence in proving relationships in colonial Massachusetts versus the Sherman transcripts which are secondary.
What do I mean by primary and secondary source evidence? Primary sources deal with recording the event either by an eyewitness to the event or transmitted to someone else to record by the eyewitness. For example, the birth of a child. The mother birthed the child and she went to the town clerk along with her husband to register the birth. When the town clerk entered the information in the register, that would be the "birth certificate" for that child. The town clerk may or may not hire other clerks to collect the registers and re-copy them into other volumes particularly in cases after a fire or other natural disasters to insure preservation of the record not only for public viewing but also for the government in determining local taxes.