Taychsoma pellionellum is a very common hypotrichous ciliate that likes to settle on the floating coverslip and can then be observed very well. However, the arrangement of the cirri on the ventral side can only be seen at high magnification. Characteristic are a right and left marginal row. On the central ventral field there are only 3 postoral cirri and 2 ventral cirri, which are arranged just in front of the 5 transversal cirri (s. fig. 2 a-c). Two macronuclei are present, between which the round micronucleus is located (s. fig. 1 c).

Tachysoma pellionellum often shows a ring-shaped, conspicuous structure in the anterior or posterior quarter of the body. This is called the fat body. It is assumed that this is a storage body. However, I was not able to detect any fat bodies in my population of Tachysoma pellionellum.

The contractile vacuole of Tachysoma pellionellum is located almost in the middle of the body on the left side (s. figs. 1 d and 2 c), which is an important distinguishing feature from the similar species Holosticha pullaster. In this species the contractile vacuole lies clearly below the middle of the body. In addition, Holosticha pullaster has 2 micronuclei instead of only one.