teloblast

from The Century Dictionary.

• noun In embryology, one of the large cells situated at the posterior growing end of the body in certain annelids and arthropods and budding forth anteriorly a row of cells which proliferates to form one of the definitive series of organs such as the nerve-chain, nephridia, and mesoblastic somites.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biology (in annelids etc) a large cell at the growing end of many embryos that produces many smaller cells