英语句子结构分析、求翻译
The nervous system of vertebrates is characterized by a hollow,dorsal nerve cord that ends in the head region as and enlargement,the brain. Even in its most primitive form this cord and its attached nerves are the result of evolutionary specialization,and their further evolution from lower to highter vertebrate classes is a process that is far from fully understood.
EVEN后面的一句就完全不会分层了,也看的不明白.求教!