1.Crabs are good to eat.The next time you have one for your supper，I should like you to look at it very carefully，and try to learn what kind of an animal it is.
2.The crab is a cousin①of the lobster and the shrimp.Like these two animals，its body is made up of a number of rings.But in the shell of the grown-up crab these rings are so close together that we cannot tell one ring from another.
3.Do you see the two short feelers which stick out in front of the crab’s head？These help the crab to find its way as it walks along the dark bottom of the sea.It has two round eyes，at the end of short eye-stalks，close to the feelers.
4.Next come the two great jointed nipping claws which you know so well；and behind these are four pairs of small jointed legs，with which the crab walks over the rocks and the sand of the sea-shore.
5.The crab‘s body inside the hard crust or shell is quite soft.The crab breathes by means of gills，with which it takes into its body some of the air which is always mixed with the sea-water.
6.While the crab is alive，it is grey and brown in colour.It only turns red，as we see it at supper，when it is boiled.
7.Crabs live in holes in the rocks near the shore.They feed on fishes，either alive or dead，and they also eat any other dead animals which they find on the sea-bottom.
8.Many crabs are found with sea-weed and even with shell-fish growing on their backs.This helps them to catch the little fishes on which they live.The fishes do not notice the crab when its shell is covered in this way.
9.The mother crab carries her eggs under her broad tail.When the young ones come out of these eggs，they are not at all like crabs，and they swim about in the sea.After a while they become like their father and mother in shape，only very much smaller.
10.But how can a crab grow when it is covered all over with a hard crust？Every year the crab throws off its old crust or shell，and a new and bigger shell soon grows in its place.
①Cousin，relation；an animal of the same kind.
11.There are many kinds of crabs.The little green crabs you see running about in the shallow①water on the sea-beach are not the same kind as the large ones which we like to eat.There arecrabs with small bodies and very long legs，called spider crabs；and there are land crabs，which spend most of their life on land.
12.When you are paddling②in the sea，do not let a crabcatch hold of your toe with its “nippers；”for these nipping-claws can give a very sore pinch indeed.See how the two crabs in the picture are fighting for a fish.How they are pinching it with their “nippers”！I wonder whichof them will get it in the end.
①Shallow，not deep.
②Paddling，playing about.
SUMMARY
The crab is of the same family as the lobster and the shrimp.It is grey and brown in colour，but when boiled it becomes red.Its body is made of a number of rings which grow so close together that we cannot tell one ring from another.It has two eyes，and its feelers help it to find its way along the dark bottom of the sea.It has two great jointed nipping claws，and four pairs of jointed legs with which it walks.It breathes by means of gills.Crabs live in holes in the rocks near the shore.They feed chiefly on fishes.Some kinds of crab are very good for food.Every year the crab throws off its shell，and a larger one soon grows.
【中文阅读】
1．螃蟹也是美味的食物。小朋友，下次你晚饭吃螃蟹的时候，请仔仔细细地观察它，了解它是一种什么动物。
2．螃蟹是龙虾和虾的近亲。①跟龙虾和虾一样，螃蟹的身体也是很多体节组成的。但是成年螃蟹的甲壳，体节彼此挨得太近，没办法分清了。②3．你看见螃蟹脑袋前面那两根短触角了吗？螃蟹在黑暗的海底爬行的时候，触角能帮它探路。触角旁边，在短短的眼柄尽头，螃蟹还长着两只圆眼睛。
4．后面就是两只你很熟悉的，分节的“钳子”，学名叫“螯（）足”。再往后是四对比较小的分节的足，螃蟹用来在海岸的石头和沙子上爬行。③5．螃蟹硬壳里面的身体很柔软。螃蟹也是用鳃呼吸的，它只用鳃吸入溶解在海水中的空气。④6．活的螃蟹是灰色和棕色的，只有在煮熟了以后，我们在吃饭的时候，才看见它是红色的。
7．螃蟹生活在河岸、海岸附近的岩洞里面，以活鱼和死鱼为食，也吃一切在海底找到的动物尸体。⑤8．人们发现很多螃蟹背上都黏着海草，甚至贝类。这些东西能帮助螃蟹抓住猎物--小鱼。蟹壳盖上了这些东西，鱼类就注意不到螃蟹了。
9．母蟹的卵就藏在宽大的“尾巴”（其实是腹部）下面。小蟹刚从卵中孵出来的时候，一点儿也不像螃蟹，在海里到处游。过了一段时间以后，样子就变得像父母了，只是个头儿小得多。⑥10．但是，螃蟹浑身都是硬壳，怎么长大呢？每年螃蟹都会扔掉旧甲壳，很快，身上就会长出新的甲壳。⑦11．螃蟹的种类很多。你看见在海滩浅水中跑来跑去的那种青色的小蟹，并不是我们爱吃的大个儿螃蟹。有一种螃蟹叫“蜘蛛蟹”，身体很小，腿却很长；还有“陆地蟹”，一生中大部分时间都是在陆地上度过的。⑧12．你在海水中走路的时候，可不要让螃蟹用“钳子”夹了脚趾头，因为螃蟹的螯足，夹人可是很痛的！看看这幅画，两只螃蟹正在争一条鱼。它们用螯足死命地抓住鱼，打得可凶了！不知最后谁能抢到这条鱼呢？
译注
①这三种动物都属于“节肢动物门”“甲壳纲”“十足目”，但“亚目”不同。
②螃蟹的身体也分为头胸部和腹部，头胸部的体节愈合在一起，腹部往前折，贴在身体下面。
③海蟹的最后一对足是扁平的，像桨一样，能用来飞快地游泳。
④这个说法太绝对了。一般人们听见“鳃”就觉得是水中的呼吸器官，其实，只要保持鳃的湿润，螃蟹是可以在陆地上活动的，这就是你看见它“口吐白沫”的时候。
⑤螃蟹的食物以鱼和其他甲壳类动物为主，但它们食性很杂。
⑥刚孵化的幼体，很像一种水生甲壳动物“水蚤”，所以叫“蚤状幼体”。蚤状幼体蜕皮5次后会长成“大眼幼体”，也叫蟹苗。蟹苗再蜕一次皮，变成幼蟹，1-2天之后甲壳才变硬。
⑦螃蟹长成幼蟹，也就是“成体”以后，寿命一般只有2-3年，一生中蜕皮也只有2-3次。
⑧螃蟹从完全水生的种类，到最适应陆地生活的种类，并没有明显的界限。陆地蟹一般指“陆蟹科”的螃蟹。此外还有“陆寄居蟹科”，代表品种是椰子蟹，是一种能长到几公斤重的庞然大物。陆地蟹是怎么呼吸的呢？前面的注释提到过，湿润的鳃可以从空气中吸收氧气。陆地蟹的鳃，结构经过特化，比水生种类的鳃更适合在空气中呼吸。而且有些种类还发展出了类似肺的器官，是一种富含血管的薄膜，位于鳃室的内表面，可以直接呼吸空气。
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