The eye on them is made from twisted gut. You can also use mono, but from what I've been told gut is the way to go. You can buy hooks that have a "return eye" like a normal hook. Why the guys who made hooks 100 years ago didn't incorporate a return eye into their hooks is beyond me, they definately had the capability to do so. Many wet flies were tied with a section of tippet tied right into the fly with no eye at all.

Also, I don't claim to be an expert on the subject, but I have been biten by the atlantic salmon bug recently and as a matter of fact just got my first big order of materials in the mail this morning. Anyways, I've been reading and reading and reading on them and hopefully that answers your question. The guy to ask is Ronn Lucas Sr. He has done a great set of tutorials here on FAOL, and just recently bought the hook making operation of Ron Reinhold. SO now Ronn Lucas is making hooks. I should have my first order of hooks from Ronn any day now. I am pretty sre he is on the FAOL sponsors list, but he has a new email address, as well as a new website. If I shouldn't be posting the links to them here I apologize and ask that a moderator remove them.

Ronn's site
http://www.ronnlucassr.com/

Ronn's new email is ronn@ronnlucassr.com

He's a great guy and is usually happy to help people out!