爱华网Eyes Of Invertebrates AndVertebrates
脊椎和无脊椎动物的的眼睛进化
December 19th, 2009
Cephalopoda possess the best eyes among invertebrates. Theirvision is in no way inferior to that of highervertebrates. Another branch of invertebrates, thearthropods, attained a high level of evolution, but, for somereason, this did not apply to their eyes. They compensated for thisshortcoming by combining a great number of ocelli (pyramids withthe base turned outwards and covered by a chitinous crystallinelens) into a few big eyes of an involved pattern, each eyeconsisting of hundreds and even thousands of such pyramids. By thejoint efforts of their individual, usually rather short-sightedocelli, insects and Crustacea can perceive the size and shape ofobjects.
头足类动物有无脊椎动物最好的眼睛。他们的视觉一点不比高级的脊椎动物差。另一类无脊椎动物是节肢动物，虽然有较高的进化，但不知为何眼睛却没有相应进化。为了补偿这种缺陷，它们用大量单眼进行组合成复眼（形如底部向外翻的金字塔，上面有一层几丁质的结晶透明层。复眼的进化形状各异，每个都有数百甚至数千单眼。在这些近视的单眼的共同作用下，昆虫和甲壳纲类动物就可以感知物理的大小和形状。
The history of the eyes of vertebrates began in a diller-entway. The otlshore area of many seas and oceans is inhabited bycurious small animals called lancelets. They look like small fishesand resemble the blade of a surgeon’s lancet, from whence theirname came. The organ of vision of the lancelet is its brain.Light-sensitive cells are scattered all along the nerve trunk ofthe lancelet which has a transparent body. It canthus differentiate between light and darkness, which is all itneeds for its way of life.
脊椎动物眼睛的历史以和耳鼻喉的进化方式类似。许多海岸居住着奇妙的小文昌鱼。它们看上去很像外科医生的手术刀。它们的视觉器官是它们的大脑。它们的身体是透明的，沿着它们的大脑神经布满了光敏细胞。这使它们能够区别白天和黑夜，对它们来说，这就足够了。
Apparently, the ancestors of the vertebrates, like lancelets,also saw with their brain. But when their bodies had lost theirtransparency, bundles of light-sensitive nerve cells had to moveotV the brain outside. This has become the pattern of the evolutionof the eyes in all vertebrates. At a certain phase in an embryo’sdevelopment two pieces separate from the brain and graduallydevelop into eyes. So, our eyes are, in fact, pieces of the brainthat have moved outside to the sunlight.
显然，脊椎动物的祖先，如文昌鱼，是用大脑来看东西的。但是，当他们的身体失去透明性后，某些光敏神经细胞不得不伸出脑外。这几乎成了所有脊椎动物眼睛进化的模式。在人类胚胎发展的某个阶段，有两瓣神经从大脑分离出来并逐渐演化成眼睛。所以说我们的眼睛事实上是我们大脑伸出来见阳光的那一部分。
The further development of the eyes in vertebratesfollowed the same pattern: they acquiredrefractive and accommodation systems and muscles which move theeye. The design became more and more involved until it resulted inour present eyes, capable of deciphering the jungles of the worstscrawl in the world and of distinguishing the slightest tints incolour. At the same time the animal brain also became more complex.The eye as such is merely a light-receiving device, like a camera.What we actually ‘see’ with is the brain. The brain pieces togetherthe information it receives from the millions of thelight-sensitive cells in the eye into a single picture. Thesnapshots made with the eye are developed in the laboratory of thebrain.
眼睛的进一步进化还是按照这种方式进行的。它们获得了屈光和光调节系统，以及为了移动眼球的肌肉。进化的结果使得我们的眼睛成为今天这个样子。今天的眼睛可以辨别无比复杂的涂鸦和感知非常细微的色彩变化。与此同时，动物的眼睛变得越来越复杂。眼睛只是个光接收器，如相机。我们实际是用大脑在“看”东西。大脑将数百万光敏细胞收集的信息拼凑起所谓图像，即图像实际上是在大脑中加工成形的。
