【考研英语原文长难句Naturalists,forinstance,wouldbeforcedtoacknowledgethattheonlydistinctionbetweenspeciesandwell-markedvarietiesisthatthelatterareknownorbelievedtobeconnectedatthepresentdaybyintermediategradati】

　　考研英语原文长难句

　　Naturalists,forinstance,wouldbeforcedtoacknowledgethattheonlydistinctionbetweenspeciesandwell-markedvarietiesisthatthelatterareknownorbelievedtobeconnectedatthepresentdaybyintermediategradations,whereasspecieswereformerly,thoughtheyarenotnow,thusconnected.

　　whereasspecieswereformerly这个分句不是没结束吗?后面怎么没有东西接啊

　　,thoughtheyarenotnow,thusconnected.是什么成分.