QuixoteCat

I'm in a bit of a conundrum with the writing sample part of the application (English doctoral program). The page limit is 15-20 pages. I'm using my undergraduate thesis, which is about 40 pages, so I'm going to need to send in an excerpt instead of the whole thing. That said, I'm stuck on what the protocol is for selecting and formatting the excerpt. Unfortunately, my thesis doesn't have chapters. It's just a long essay. So, instead of selecting chapters, would it look unprofessional or lazy of me to just send in the first 20 pages, with a summary/explanation on the cover? The first 20 pages are probably the strongest part of the thesis, anyway, but I feel worried that I'll look slapdash, or that the committee will see my sample and think, "Why doesn't this moron have chapters?" Yikes. Thanks in advance.