What is your SG? is it checked with a hydrometer or refractometer? If tested with a hydrometer, how long have you owned it? Your SG needs to be at 1.025 or 1.026.

What is the temp of your tank?

E. Quadricolors split when ever they are over fed, get too large or when stressed by low quality water. I can't tell you when its going to split just what causes them to split on their own.

As for long tentacle anemones M. Doreensis. They don't split..they only reproduce sexually. No one has ever reported M. Doreensis to reproduce asexually.

What you have looks like a E. Quadricolor with no bubble tips. They tend to lose their bubble or bulb tips in captivity.

I don't know what has caused your anemone to look like that but it might help if you would post your tank parameters.

How long has your tank been established before you added this anemone?
What kind of lights do you have?