21. as my own studies have advanced，i have been increasingly impressed with the functional similarities between insect and vertebrate societies and less so with the structural differences that seem，at first glance，to constitute such an immense gulf between them. (5)
译文： 随着我的研究不断深入，我对昆虫和脊椎动物群落之间的功能类似性印象愈来愈深刻，而对结构上的差异印象愈发淡漠，虽然这些结构上的差异初看上去似乎构成了二者间一条无法愈越的鸿沟。
难句类型： 复杂修饰、插入语、省略
解释： 本句子的中间一段impressed with the functional similarites between insect and vertebrate societies and less so with the structural differences容易令人看晕，其中的insect and vertebrate societies and less so with由两个and连接了三个部分，然而它们其实不是同一层次的并列，第一个and实际上是between insect societies and vertebrate societies的一部分，是并列的，而and之后的less so with其实是对于一个完整的表达方式i have been increasingly less impressed with的省略形式，去掉了与前面重复的成分。
后面修饰的 structural differences的定语从句that seem, at first glance, to constitute such an immense gulf between them中，又出现了一个别扭的插入语at first glance，把应该连在一起的seem to 粗暴地分开，令人不熟悉此类难句的人倍感不适。
意群训练： as my own studies have advanced, i have been increasingly impressed with the functional similarities between insect and vertebrate societies and less so with the structural differences that seem, at first glance, to constiture such an immense gulf between them.
22. although fiction assuredly springs from political circumstances，its authors react to those circumstances in ways other than ideological，an...