The tunic with long sleeves (tunica manicata) was a later fashion.
The tunica, a loose sack-like tunic with a hole for the head, was the innermost garment worn by all classes of Roman citizens under the republic and empire.
It was either sleeveless (colobium) or sleeved (tunica manicata or manuleata), and originally fell about to the knee, but later on reached to the ankles (tunica talaris).
The tunica was originally of white wool, but in the 3rd century it began to be made of linen, and from the 4th century was always of linen.
About the 6th century the long tunica alba went out of fashion in civil life, but it was retained in the services of the Church and developed into the various forms of the liturgical alb (q.v.) and surplice (q.v.).