Book IV chapter 8

All the Crustacea can crawl as well as swim, and accordingly they are provided with numerous feet. There are four main genera, viz. the Carabi, as they are called, the Astaci, the Carides, and the Carcini. In each of these genera, again, there are numerous species, which differ from each other not only as regards shape, but also very considerably¹ as regards size. For, while in some species the individuals are large, in others they are excessively minute. The Carcinoid and Caraboid Crustacea resemble each other in possessing claws. These claws are not for locomotion², but to serve in place of hands for seizing and holding objects; and they are therefore bent³ in the opposite direction to the feet, being so twisted as to turn their convexity towards the body, while their feet turn towards it their concavity. For in this position the claws are best suited for laying hold of the food and carrying it to the mouth. The distinction between the Carabi and the Carcini (Crabs⁴) consists in the former having a tail while the latter have none. For the Carabi swim about and a tail is therefore of use to them, serving for their propulsion like the blade of an oar⁵. But it would be of no use to the Crabs; for these animals live habitually⁶ close to the shore, and creep into holes and corners. In such of them as live out at sea, the feet are much less adapted for locomotion than in the rest, because they are little given to moving about but depend for protection on their shell-like covering. The Maiae and the crabs known as Heracleotic are examples of this; the legs in the former being very thin, in the latter very short.

The very minute crabs that are found among the small fry at the bottom of the net have their hindermost feet flattened⁷ out into the semblance⁸ of fins⁹ or oar-blades, so as to help the animal in swimming.

The Carides are distinguished¹⁰ from the Carcinoid species by the presence of a tail; and from the Caraboids by the absence of claws. This is explained by their large number of feet, on which has been expended¹¹ the material for the growth of claws. Their feet again are numerous to suit their mode of progression, which is mainly by swimming.

Of the parts on the ventral surface, those near the head are in some of these animals formed like gills, for the admission and discharge of water; while the parts lower down differ in the two sexes. For in the female Carabi these are more laminar than in the males, and in the female crabs the flap is furnished with hairier appendages¹². This gives ampler space for the disposal of the ova, which the females retain in these parts instead of letting them go free, as do fishes and all other oviparous animals. In the Carabi and in the Crabs the right claw is invariably the larger and the stronger. For it is natural to every animal in active operations to use the parts on its right side in preference to those on its left; and nature, in distributing the organs, invariably assigns each, either exclusively or in a more perfect condition, to such animals as can use it. So it is with tusks¹³, and teeth, and horns, and spurs, and all such defensive¹⁴ and offensive weapons.

In the Lobsters¹⁵ alone it is a matter of chance which claw is the larger, and this in either sex. Claws they must have, because they belong to a genus in which this is a constant character; but they have them in this indeterminate way, owing to imperfect formation and to their not using them for their natural purpose, but for locomotion.

For a detailed¹⁶ account of the several parts of these animals, of their position and their differences, those parts being also included which distinguish the sexes, reference must be made to the treatises¹⁷ on Anatomy¹⁸ and to the Researches concerning Animals.

1 considerably   

adv.极大地；相当大地；在很大程度上

参考例句：

• The economic situation has changed considerably.经济形势已发生了相当大的变化。
• The gap has narrowed considerably.分歧大大缩小了。

2 locomotion   

n.运动，移动

参考例句：

• By land,air or sea,birds are masters of locomotion.无论是通过陆地，飞越空中还是穿过海洋，鸟应算是运动能手了。
• Food sources also elicit oriented locomotion and recognition behavior patterns in most insects.食物源也引诱大多数昆虫定向迁移和识别行为。

3 bent   

n.爱好，癖好；adj.弯的；决心的，一心的

参考例句：

• He was fully bent upon the project.他一心扑在这项计划上。
• We bent over backward to help them.我们尽了最大努力帮助他们。

4 crabs   

n.蟹( crab的名词复数 )；阴虱寄生病；蟹肉v.捕蟹( crab的第三人称单数 )

参考例句：

• As we walked along the seashore we saw lots of tiny crabs. 我们在海岸上散步时看到很多小蟹。 来自《简明英汉词典》
• The fish and crabs scavenge for decaying tissue. 鱼和蟹搜寻腐烂的组织为食。 来自《简明英汉词典》

5 oar   

n.桨，橹，划手；v.划行

参考例句：

• The sailors oar slowly across the river.水手们慢慢地划过河去。
• The blade of the oar was bitten off by a shark.浆叶被一条鲨鱼咬掉了。

6 habitually   

ad.习惯地，通常地

参考例句：

• The pain of the disease caused him habitually to furrow his brow. 病痛使他习惯性地紧皱眉头。
• Habitually obedient to John, I came up to his chair. 我已经习惯于服从约翰，我来到他的椅子跟前。

7 flattened   

[医]（水）平扁的，弄平的

参考例句：

• She flattened her nose and lips against the window. 她把鼻子和嘴唇紧贴着窗户。
• I flattened myself against the wall to let them pass. 我身体紧靠着墙让他们通过。

8 semblance   

n.外貌，外表

参考例句：

• Her semblance of anger frightened the children.她生气的样子使孩子们感到害怕。
• Those clouds have the semblance of a large head.那些云的形状像一个巨大的人头。

9 fins   

[医]散热片；鱼鳍；飞边；鸭掌

参考例句：

• The level of TNF-α positively correlated with BMI,FPG,HbA1C,TG,FINS and IRI,but not with SBP and DBP. TNF-α水平与BMI、FPG、HbA1C、TG、FINS和IRI呈显著正相关，与SBP、DBP无相关。 来自互联网
• Fins are a feature specific to fish. 鱼鳍是鱼类特有的特征。 来自辞典例句

10 distinguished   

adj.卓越的，杰出的，著名的

参考例句：

• Elephants are distinguished from other animals by their long noses.大象以其长长的鼻子显示出与其他动物的不同。
• A banquet was given in honor of the distinguished guests.宴会是为了向贵宾们致敬而举行的。

11 expended   

v.花费( expend的过去式和过去分词 )；使用（钱等）做某事；用光；耗尽

参考例句：

• She expended all her efforts on the care of home and children. 她把所有精力都花在料理家务和照顾孩子上。
• The enemy had expended all their ammunition. 敌人已耗尽所有的弹药。 来自《简明英汉词典》

12 appendages   

n.附属物( appendage的名词复数 )；依附的人；附属器官；附属肢体（如臂、腿、尾等）

参考例句：

• The 11th segment carries a pair of segmented appendages, the cerci. 第十一节有一对分节的附肢，即尾须。 来自辞典例句
• Paired appendages, with one on each side of the body, are common in many animals. 很多动物身上有成对的附肢，一侧一个，这是很普遍的现象。 来自辞典例句

13 tusks   

n.（象等动物的）长牙( tusk的名词复数 )；獠牙；尖形物；尖头

参考例句：

• The elephants are poached for their tusks. 为获取象牙而偷猎大象。
• Elephant tusks, monkey tails and salt were used in some parts of Africa. 非洲的一些地区则使用象牙、猴尾和盐。 来自英语晨读30分（高一）

14 defensive   

adj.防御的；防卫的；防守的

参考例句：

• Their questions about the money put her on the defensive.他们问到钱的问题，使她警觉起来。
• The Government hastily organized defensive measures against the raids.政府急忙布置了防卫措施抵御空袭。

15 lobsters   

龙虾( lobster的名词复数 )； 龙虾肉

参考例句：

• I have no idea about how to prepare those cuttlefish and lobsters. 我对如何烹调那些乌贼和龙虾毫无概念。
• She sold me a couple of live lobsters. 她卖了几只活龙虾给我。

16 detailed   

adj.详细的，详尽的，极注意细节的，完全的

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。

17 treatises   

n.专题著作，专题论文，专著( treatise的名词复数 )

参考例句：

• Many treatises in different languages have been published on pigeons. 关于鸽类的著作，用各种文字写的很多。 来自辞典例句
• Many other treatises incorporated the new rigor. 许多其它的专题论文体现了新的严密性。 来自辞典例句

18 anatomy   

n.解剖学，解剖；功能，结构，组织

参考例句：

• He found out a great deal about the anatomy of animals.在动物解剖学方面，他有过许多发现。
• The hurricane's anatomy was powerful and complex.对飓风的剖析是一项庞大而复杂的工作。