While species vary considerably in size and shape, most are easily identified by their red or pinkish color, which is caused by granules of the pigment blepharismin.

[1] All members of the genus possess a long series of membranelles on the left side of the oral groove, and an "undulating membrane" (a structure resembling a flap, scarf or small sail, composed of long cilia fused together as a single sheet) on the right side of the peristome, toward the posterior.

Since some varieties are easily cultured and readily available from scientific supply houses, they are a common object of study in school science classes.

Depending on species and phase of life, they may be rod-shaped, ovoid, spherical, or moniliform (like a rosary, or string of beads).

[6] In Blepharisma, as in some other ciliates, chemical substances called gamones are used to induce conjugation by stimulating interaction between compatible mating partners.

Conjugation of opposite mating types promotes outcrossing and the masking of deleterious recessive mutations in the diploid phase of the sexual cycle.

When individuals are given a diet of smaller Blepharisma, or certain ciliates (particularly Colpidium colpoda or Tetrahymena), they grow to a relatively enormous size.

The ability to detect light is accomplished with photosensitive pigment granules located just under the plasma membrane of the cell.