IP headers twice with ICMP packet

[zillah]

While I was reading The "TCP/IP Protocol Suite" by Forouzan

I found that ICMP packet has got two ip headers ,,,,why ?

Source for image below is chapter 09 from this link :
http://www.mhhe.com/engcs/compsci/forouzan/tcpipppt.mhtml

http://img79.imageshack.us/img79/6214/ipheadertwice2ol.jpg (http://imageshack.us)