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1.   Let us now briefly consider the steps by which domestic races have been produced, either from one or from several allied species. Some little effect may, perhaps, be attributed to the direct action of the external conditions of life, and some little to habit; but he would be a bold man who would account by such agencies for the differences of a dray and race horse, a greyhound and bloodhound, a carrier and tumbler pigeon. One of the most remarkable features in our domesticated races is that we see in them adaptation, not indeed to the animal's or plant's own good, but to man's use or fancy. Some variations useful to him have probably arisen suddenly, or by one step; many botanists, for instance, believe that the fuller's teazle, with its hooks, which cannot be rivalled by any mechanical contrivance, is only a variety of the wild Dipsacus; and this amount of change may have suddenly arisen in a seedling. So it has probably been with the turnspit dog; and this is known to have been the case with the ancon sheep. But when we compare the dray-horse and race-horse, the dromedary and camel, the various breeds of sheep fitted either for cultivated land or mountain pasture, with the wool of one breed good for one purpose, and that of another breed for another purpose; when we compare the many breeds of dogs, each good for man in very different ways; when we compare the gamecock, so pertinacious in battle, with other breeds so little quarrelsome, with 'everlasting layers' which never desire to sit, and with the bantam so small and elegant; when we compare the host of agricultural, culinary, orchard, and flower-garden races of plants, most useful to man at different seasons and for different purposes, or so beautiful in his eyes, we must, I think, look further than to mere variability. We cannot suppose that all the breeds were suddenly produced as perfect and as useful as we now see them; indeed, in several cases, we know that this has not been their history. The key is man's power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to make for himself useful breeds.The great power of this principle of selection is not hypothetical. It is certain that several of our eminent breeders have, even within a single lifetime, modified to a large extent some breeds of cattle and sheep. In order fully to realise what they have done, it is almost necessary to read several of the many treatises devoted to this subject, and to inspect the animals. Breeders habitually speak of an animal's organisation as something quite plastic, which they can model almost as they please. If I had space I could quote numerous passages to this effect from highly competent authorities. Youatt, who was probably better acquainted with the works of agriculturalists than almost any other individual, and who was himself a very good judge of an animal, speaks of the principle of selection as 'that which enables the agriculturist, not only to modify the character of his flock, but to change it altogether. It is the magician's wand, by means of which he may summon into life whatever form and mould he pleases.' Lord Somerville, speaking of what breeders have done for sheep, says: 'It would seem as if they had chalked out upon a wall a form perfect in itself, and then had given it existence.' That most skilful breeder, Sir John Sebright, used to say, with respect to pigeons, that 'he would produce any given feather in three years, but it would take him six years to obtain head and beak.' In Saxony the importance of the principle of selection in regard to merino sheep is so fully recognised, that men follow it as a trade: the sheep are placed on a table and are studied, like a picture by a connoisseur; this is done three times at intervals of months, and the sheep are each time marked and classed, so that the very best may ultimately be selected for breeding.What English breeders have actually effected is proved by the enormous prices given for animals with a good pedigree; and these have now been exported to almost every quarter of the world. The improvement is by no means generally due to crossing different breeds; all the best breeders are strongly opposed to this practice, except sometimes amongst closely allied sub-breeds. And when a cross has been made, the closest selection is far more indispensable even than in ordinary cases. If selection consisted merely in separating some very distinct variety, and breeding from it, the principle would be so obvious as hardly to be worth notice; but its importance consists in the great effect produced by the accumulation in one direction, during successive generations, of differences absolutely inappreciable by an uneducated eye differences which I for one have vainly attempted to appreciate. Not one man in a thousand has accuracy of eye and judgement sufficient to become an eminent breeder. If gifted with these qualities, and he studies his subject for years, and devotes his lifetime to it with indomitable perseverance, he will succeed, and may make great improvements; if he wants any of these qualities, he will assuredly fail. Few would readily believe in the natural capacity and years of practice requisite to become even a skilful pigeon-fancier.The same principles are followed by horticulturists; but the variations are here often more abrupt. No one supposes that our choicest productions have been produced by a single variation from the aboriginal stock. We have proofs that this is not so in some cases, in which exact records have been kept; thus, to give a very trifling instance, the steadily-increasing size of the common gooseberry may be quoted. We see an astonishing improvement in many florists' flowers, when the flowers of the present day are compared with drawings made only twenty or thirty years ago. When a race of plants is once pretty well established, the seed-raisers do not pick out the best plants, but merely go over their seed-beds, and pull up the 'rogues,' as they call the plants that deviate from the proper standard. With animals this kind of selection is, in fact, also followed; for hardly any one is so careless as to allow his worst animals to breed.
2. 在1984年的民主党党魁选举上,杰西·杰克逊(JesseJackson)的支持者们遇到了利用选票发送信号的问题。他们早就估计到杰西不可能胜出。民意调查显示,加里·哈特(GaryHart)和沃尔特·蒙代尔遥遥领先。这时出现了一种激励,要求选民把票投给遥遥领先者,以免浪费自己的选票。这个问题到了1988年争取民主党总统候选人提名的时候更是变本加厉,因为当时有7个候选人竞争民主党总统候选人的资格。支持者们不想把自己的选票或竞选资助款项浪费在毫无希望的候选人身上。这么一来,那些宣布谁正领先的民意调查和媒体报道,就有了左右局势、使自己的预言变成现实的真正潜力。
3.  在会场上,你可以看到数百人同时跳舞的超会议最热闹的“超舞见区域”;在《白箱》声优体验活动上,你可以在录音棚使用专业设备和工作人员准备好的台本,给喜欢的人物配音;去年的niconico超会议还首次上演了歌舞伎舞者与Vocaloid角色合作的全新歌舞伎形态的“超歌舞伎”——初音名曲《千本樱》与歌舞伎代表作之一的《义经千本樱》的联合新作《今昔飨宴千本樱》。
4. 家住岳阳市的毛女士就被一个小小的口罩难倒了。
5.   'Time will go fast with you, Mr. Jack Maldon,' pursued the Doctor, 'and fast with all of us. Some of us can hardly expect, perhaps, in the natural course of things, to greet you on your return. The next best thing is to hope to do it, and that's my case. I shall not weary you with good advice. You have long had a good model before you, in your cousin Annie. Imitate her virtues as nearly as you can.'
6. 保证空调系统或排气扇运转正常,定期清洗空调滤网,加强开窗通风换气。

文库

1. 战略指北针和战略支点相辅相成,是瞄准工具,用来衡量每个动作战略价值的准星。
2. 展开全文MAIAACTIVE玛娅是一个设计师运动品牌,该品牌联合创始人兼CEO王佳音曾是维多利亚的秘密纽约总部第一位亚裔买手,她告诉记者大品牌的新一季产品往往都是提前一年计划的,但在这一年的时间里,消费者的需求会发生很多变化,等到产品真正推出已经无法满足新需求。
3. 一时间,德国的核能开发工程呈现一片繁荣景象。
4.   I HAVE hitherto sometimes spoken as if the variations so common and multiform in organic beings under domestication, and in a lesser degree in those in a state of nature had been due to chance. This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation. Some authors believe it to be as much the function of the reproductive system to produce individual differences, or very slight deviations of structure, as to make the child like its parents. But the much greater variability, as well as the greater frequency of monstrosities, under domestication or cultivation, than under nature, leads me to believe that deviations of structure are in some way due to the nature of the conditions of life, to which the parents and their more remote ancestors have been exposed during several generations. I have remarked in the first chapter but a long catalogue of facts which cannot be here given would be necessary to show the truth of the remark that the reproductive system is eminently susceptible to changes in the conditions of life; and to this system being functionally disturbed in the parents, I chiefly attribute the varying or plastic condition of the offspring. The male and female sexual elements seem to be affected before that union takes place which is to form a new being. In the case of 'sporting' plants, the bud, which in its earliest condition does not apparently differ essentially from an ovule, is alone affected. But why, because the reproductive system is disturbed, this or that part should vary more or less, we are profoundly ignorant. Nevertheless, we can here and there dimly catch a faint ray of light, and we may feel sure that there must be some cause for each deviation of structure, however slight.How much direct effect difference of climate, food, &c., produces on any being is extremely doubtful. My impression is, that the effect is extremely small in the case of animals, but perhaps rather more in that of plants. We may, at least, safely conclude that such influences cannot have produced the many striking and complex co-adaptations of structure between one organic being and another, which we see everywhere throughout nature. Some little influence may be attributed to climate, food, &c.: thus, E. Forbes speaks confidently that shells at their southern limit, and when living in shallow water, are more brightly coloured than those of the same species further north or from greater depths. Gould believes that birds of the same species are more brightly coloured under a clear atmosphere, than when living on islands or near the coast. So with insects, Wollaston is convinced that residence near the sea affects their colours. Moquin-Tandon gives a list of plants which when growing near the sea-shore have their leaves in some degree fleshy, though not elsewhere fleshy. Several other such cases could be given.The fact of varieties of one species, when they range into the zone of habitation of other species, often acquiring in a very slight degree some of the characters of such species, accords with our view that species of all kinds are only well-marked and permanent varieties. Thus the species of shells which are confined to tropical and shallow seas are generally brighter-coloured than those confined to cold and deeper seas. The birds which are confined to continents are, according to Mr Gould, brighter-coloured than those of islands. The insect-species confined to sea-coasts, as every collector knows, are often brassy or lurid. Plants which live exclusively on the sea-side are very apt to have fleshy leaves. He who believes in the creation of each species, will have to say that this shell, for instance, was created with bright colours for a warm sea; but that this other shell became bright-coloured by variation when it ranged into warmer or shallower waters.
5.   "You'll have to send in your card."
6. We are used to seeing what we call "a mother" completely wrapped up in her own pink bundle of fascinating babyhood, and taking but the faintest theoretic interest in anybody else's bundle, to say nothing of the common needs of ALL the bundles. But these women were working all together at the grandest of tasks--they were Making People--and they made them well.

推荐功能

1. 据WhaTech预测,2020年全球NLP市场将达到134亿美元。
2. 清代,农作物的种植,有不同程度的改进。有些经济作物和高产的粮食作物,得到一定的推广。其中高产的粮食作物主要是水稻、甘薯和玉蜀黍,经济作物则主要是烟草、棉花、甘蔗和蚕桑。
3. We will develop cultural programs and industries.
4.   "And on what occasion?"
5. 此举在中国社交媒体上引发热烈讨论,这名女孩被称为最美日本女孩。
6.   At length, came to the hand of one, who had three sonnes, all ofthem goodly and vertuous persons, and verie obedient to theirFather: in which regard, he affected them all equally, without anydifference or partiall respect. The custome of this Ring beingknowne to them, each one of them (coveting to beare esteeme abovethe other) desired (as hee could best make his meanes) his Father,that in regard he was now growne very old, he would leave that Ring tohim, whereby he should bee acknowledged for his heire. The good man,who loved no one of them more then the other, knew not how to make hischoise, nor to which of them he should leave the Ring: yet having pasthis promise to them severally, he studied by what meanes to satisfiethem all three. Wherefore, secretly having conferred with a curiousand excellent Goldsmith, hee caused two other Rings to bee made, soreally resembling the first made Ring, that himselfe (when he had themin his hand) could not distinguish which was the right one.

应用

1. 他早在1848年就向上院商业危机调查委员会一再说到,
2. 他将自己关进了家里的主卧室,进行自我隔离,自己和家人在家都戴着口罩和手套,家人会将做好的饮食放在他的门口。
3. 当时,有人在网上发文,题目为《高铁确实辐射严重,未婚女性少坐》,称国产高铁从诞生起就存在严重的辐射问题,坐高铁等同于照X光,对人最大的危害就是破坏女性生殖系统。
4.   On the view here given of the all-important part which selection by man has played, it becomes at once obvious, how it is that our domestic races show adaptation in their structure or in their habits to man's wants or fancies. We can, I think, further understand the frequently abnormal character of our domestic races, and likewise their differences being so great in external characters and relatively so slight in internal parts or organs. Man can hardly select, or only with much difficulty, any deviation of structure excepting such as is externally visible; and indeed he rarely cares for what is internal. He can never act by selection, excepting on variations which are first given to him in some slight degree by nature. No man would ever try to make a fantail, till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter till he saw a pigeon with a crop of somewhat unusual size; and the more abnormal or unusual any character was when it first appeared, the more likely it would be to catch his attention. But to use such an expression as trying to make a fantail, is, I have no doubt, in most cases, utterly incorrect. The man who first selected a pigeon with a slightly larger tail, never dreamed what the descendants of that pigeon would become through long-continued, partly unconscious and partly methodical selection. Perhaps the parent bird of all fantails had only fourteen tail-feathers somewhat expanded, like the present Java fantail, or like individuals of other and distinct breeds, in which as many as seventeen tail-feathers have been counted. Perhaps the first pouter-pigeon did not inflate its crop much more than the turbit now does the upper part of its oesophagus, a habit which is disregarded by all fanciers, as it is not one of the points of the breed.Nor let it be thought that some great deviation of structure would be necessary to catch the fancier's eye: he perceives extremely small differences, and it is in human nature to value any novelty, however slight, in one's own possession. Nor must the value which would formerly be set on any slight differences in the individuals of the same species, be judged of by the value which would now be set on them, after several breeds have once fairly been established. Many slight differences might, and indeed do now, arise amongst pigeons, which are rejected as faults or deviations from the standard of perfection of each breed. The common goose has not given rise to any marked varieties; hence the Thoulouse and the common breed, which differ only in colour, that most fleeting of characters, have lately been exhibited as distinct at our poultry-shows.
5. 原标题:4岁男孩走失后冻僵警察蜀黍找到他急忙捂在怀里近日,在江西九江修水县港口镇一名4岁男孩意外走失,当地民警和群众立即展开相救,男孩被找到时已经昏迷失去意识,但民警和群众持续的暖心相救,最终让男孩化险为夷。
6.   Chapter XLIV

旧版特色

1.   Faust
2. 这个病例的流行病史调查十分清晰,它再次提醒市民朋友:重点地区来沪人员一定要及时主动申报。
3. 对此您怎么看?金灿荣:根据我的观察,我们的舆论最大焦点还是在控制疫情本身,这一点很好,另外大家好像还很关心谁的责任,一开始怪地方政府,现在好像又怪到专家头上去了,另外红十字会也是一个焦点——网上不同群体相互指责,截止到今天网上的正能量非常多的,负能量也是不少,谣言满天飞,各种幸灾乐祸,制造恐慌的人也非常多。

网友评论(27128 / 58169 )

  • 1:常天童 2020-07-20 07:06:23

    熟悉学生特点,教育教学经验丰富,对学生培养体系具有较深的理解。

  • 2:李少波 2020-07-20 07:06:23

    有询问酒店住宿情况的,有打听隔离天数的。

  • 3:朱拱拱 2020-07-24 07:06:23

    阅读全文为了让被投企业活下去,投资人忙疯了本来约在机场聊投资,投资人却带着好几个他投过的企业创始人,希望我们能达成合作。

  • 4:蒋干 2020-07-29 07:06:23

    同时,柳林县教育科技局对柳林县创新双语学校管理中存在问题及相关责任人作出了处理意见,责令学校对涉案教师予以解聘,按程序依法撤销其教师资格,责令校董事会对校长按程序予以解聘处理。

  • 5:林恩贝 2020-07-22 07:06:23

    其实,除夕那天梁述光就已经发布了一张为武汉加油的作品,上面是一位全副武装的医护人员。

  • 6:邓振春 2020-08-04 07:06:23

    我们知道,很多时候企业网站的变化是因为外部环境而改变最初的想法的。

  • 7:泰莱托维奇 2020-08-03 07:06:23

    我们可以相当确定人类会向神性迈进,因为人类有太多理由渴望这样的进化,而且也有太多方式能够达到这样的目标。就算某条原本看来很有希望的路其实是条死胡同,仍然能有其他替代路线。举例来说,我们可能发现人类基因组实在太复杂,无法进行更进一步的操作,但这并不影响我们继续开发脑机接口(brain-computerinterface)、纳米机器人或人工智能。

  • 8:倪海雄 2020-08-03 07:06:23

      `And mind you!' said Mr. Cruncher. `No games tomorrow! If I, as a honest tradesman, succeed in providing a jinte of meat or two, none of your not touching of it, and sticking to bread. If I, as a honest tradesman, am able to provide a little beer, none of your declaring on water. When you go to Rome, do as Rome does. Rome will be a ugly customer to you, if you don't. `I'm your Rome, you know.'

  • 9:陈晋 2020-07-20 07:06:23

      "He is changed into a black stone," answered the dervish, "like all the rest who have gone on the same errand, and you will become one likewise if you are not more careful in following my directions." Then he charged the prince, as he valued his life, to take no heed of the clamour of voices that would pursue him up the mountain, and handing him a ball from the bag, which still seemed to be half full, he sent him on his way.

  • 10:布拉加德 2020-07-28 07:06:23

    元朝统一了吐蕃,吐蕃封建农奴制社会得到新的发展。

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