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1.   That varieties of this doubtful nature are far from uncommon cannot be disputed. Compare the several floras of Great Britain, of France or of the United States, drawn up by different botanists, and see what a surprising number of forms have been ranked by one botanist as good species, and by another as mere varieties. Mr H. C. Watson, to whom I lie under deep obligation for assistance of all kinds, has marked for me 182 British plants, which are generally considered as varieties, but which have all been ranked by botanists as species; and in making this list he has omitted many trifling varieties, but which nevertheless have been ranked by some botanists as species, and he has entirely omitted several highly polymorphic genera. Under genera, including the most polymorphic forms, Mr Babington gives 251 species, whereas Mr Bentham gives only 112, a difference of 139 doubtful forms! Amongst animals which unite for each birth, and which are highly locomotive, doubtful forms, ranked by one zoologist as a species and by another as a variety, can rarely be found within the same country, but are common in separated areas. How many of those birds and insects in North America and Europe, which differ very slightly from each other, have been ranked by one eminent naturalist as undoubted species, and by another as varieties, or, as they are often called, as geographical races! Many years ago, when comparing, and seeing others compare, the birds from the separate islands of the Galapagos Archipelago, both one with another, and with those from the American mainland, I was much struck how entirely vague and arbitrary is the distinction between species and varieties. On the islets of the little Madeira group there are many insects which are characterized as varieties in Mr Wollaston's admirable work, but which it cannot be doubted would be ranked as distinct species by many entomologists. Even Ireland has a few animals, now generally regarded as varieties, but which have been ranked as species by some zoologists. Several most experienced ornithologists consider our British red grouse as only a strongly-marked race of a Norwegian species, whereas the greater number rank it as an undoubted species peculiar to Great Britain. A wide distance between the homes of two doubtful forms leads many naturalists to rank both as distinct species; but what distance, it has been well asked, will suffice? if that between America and Europe is ample, will that between the Continent and the Azores, or Madeira, or the Canaries, or Ireland, be sufficient? It must be admitted that many forms, considered by highly-competent judges as varieties, have so perfectly the character of species that they are ranked by other highly-competent judges as good and true species. But to discuss whether they are rightly called species or varieties, before any definition of these terms has been generally accepted, is vainly to beat the air.Many of the cases of strongly-marked varieties or doubtful species well deserve consideration; for several interesting lines of argument, from geographical distribution, analogical variation, hybridism, &c., have been brought to bear on the attempt to determine their rank. I will here give only a single instance, the well-known one of the primrose and cowslip, or Primula veris and elatior. These plants differ considerably in appearance; they have a different flavour and emit a different odour; they flower at slightly different periods; they grow in somewhat different stations; they ascend mountains to different heights; they have different geographical ranges; and lastly, according to very numerous experiments made during several years by that most careful observer G?rtner, they can be crossed only with much difficulty. We could hardly wish for better evidence of the two forms being specifically distinct. On the other hand, they are united by many intermediate links, and it is very doubtful whether these links are hybrids; and there is, as it seems to me, an overwhelming amount of experimental evidence, showing that they descend from common parents, and consequently must be ranked as varieties.Close investigation, in most cases, will bring naturalists to an agreement how to rank doubtful forms. Yet it must be confessed, that it is in the best-known countries that we find the greatest number of forms of doubtful value. I have been struck with the fact, that if any animal or plant in a state of nature be highly useful to man, or from any cause closely attract his attention, varieties of it will almost universally be found recorded. These varieties, moreover, will be often ranked by some authors as species. Look at the common oak, how closely it has been studied; yet a German author makes more than a dozen species out of forms, which are very generally considered as varieties; and in this country the highest botanical authorities and practical men can be quoted to show that the sessile and pedunculated oaks are either good and distinct species or mere varieties.
2.   When we see any part or organ developed in a remarkable degree or manner in any species, the fair presumption is that it is of high importance to that species; nevertheless the part in this case is eminently liable to variation. Why should this be so? On the view that each species has been independently created, with all its parts as we now see them, I can see no explanation. But on the view that groups of species have descended from other species, and have been modified through natural selection, I think we can obtain some light. In our domestic animals, if any part, or the whole animal, be neglected and no selection be applied, that part (for instance, the comb in the Dorking fowl) or the whole breed will cease to have a nearly uniform character. The breed will then be said to have degenerated. In rudimentary organs, and in those which have been but little specialized for any particular purpose, and perhaps in polymorphic groups, we see a nearly parallel natural case; for in such cases natural selection either has not or cannot come into full play, and thus the organisation is left in a fluctuating condition. But what here more especially concerns us is, that in our domestic animals those points, which at the present time are undergoing rapid change by continued selection, are also eminently liable to variation. Look at the breeds of the pigeon; see what a prodigious amount of difference there is in the beak of the different tumblers, in the beak and wattle of the different carriers, in the carriage and tail of our fantails, &c., these being the points now mainly attended to by English fanciers. Even in the sub-breeds, as in the short-faced tumbler, it is notoriously difficult to breed them nearly to perfection, and frequently individuals are born which depart widely from the standard. There may be truly said to be a constant struggle going on between, on the one hand, the tendency to reversion to a less modified state, as well as an innate tendency to further variability of all kinds, and, on the other hand, the power of steady selection to keep the breed true. In the long run selection gains the day, and we do not expect to fail so far as to breed a bird as coarse as a common tumbler from a good short-faced strain. But as long as selection is rapidly going on, there may always be expected to be much variability in the structure undergoing modification. It further deserves notice that these variable characters, produced by man's selection, sometimes become attached, from causes quite unknown to us, more to one sex than to the other, generally to the male sex, as with the wattle of carriers and the enlarged crop of pouters.Now let us turn to nature. When a part has been developed in an extraordinary manner in any one species, compared with the other species of the same genus, we may conclude that this part has undergone an extraordinary amount of modification, since the period when the species branched off from the common progenitor of the genus. This period will seldom be remote in any extreme degree, as species very rarely endure for more than one geological period. An extraordinary amount of modification implies an unusually large and long-continued amount of variability, which has continually been accumulated by natural selection for the benefit of the species. But as the variability of the extraordinarily-developed part or organ has been so great and long-continued within a period not excessively remote, we might, as a general rule, expect still to find more variability in such parts than in other parts of the organisation, which have remained for a much longer period nearly constant. And this, I am convinced, is the case. That the struggle between natural selection on the one hand, and the tendency to reversion and variability on the other hand, will in the course of time cease; and that the most abnormally developed organs may be made constant, I can see no reason to doubt. Hence when an organ, however abnormal it may be, has been transmitted in approximately the same condition to many modified descendants, as in the case of the wing of the bat, it must have existed, according to my theory, for an immense period in nearly the same state; and thus it comes to be no more variable than any other structure. It is only in those cases in which the modification has been comparatively recent and extraordinarily great that we ought to find the generative variability, as it may be called, still present in a high degree. For in this case the variability will seldom as yet have been fixed by the continued selection of the individuals varying in the required manner and degree, and by the continued rejection of those tending to revert to a former and less modified condition.The principle included in these remarks may be extended. It is notorious that specific characters are more variable than generic. To explain by a simple example what is meant. If some species in a large genus of plants had blue flowers and some had red, the colour would be only a specific character, and no one would be surprised at one of the blue species varying into red, or conversely; but if all the species had blue flowers, the colour would become a generic character, and its variation would be a more unusual circumstance. I have chosen this example because an explanation is not in this case applicable, which most naturalists would advance, namely, that specific characters are more variable than generic, because they are taken from parts of less physiological importance than those commonly used for classing genera. I believe this explanation is partly, yet only indirectly, true; I shall, however, have to return to this subject in our chapter on Classification. It would be almost superfluous to adduce evidence in support of the above statement, that specific characters are more variable than generic; but I have repeatedly noticed in works on natural history, that when an author has remarked with surprise that some important organ or part, which is generally very constant throughout large groups of species, has differed considerably in closely-allied species, that it has, also, been variable in the individuals of some of the species. And this fact shows that a character, which is generally of generic value, when it sinks in value and becomes only of specific value, often becomes variable, though its physiological importance may remain the same. Something of the same kind applies to monstrosities: at least Is. Geoffroy St. Hilaire seems to entertain no doubt, that the more an organ normally differs in the different species of the same group, the more subject it is to individual anomalies.On the ordinary view of each species having been independently created, why should that part of the structure, which differs from the same part in other independently-created species of the same genus, be more variable than those parts which are closely alike in the several species? I do not see that any explanation can be given. But on the view of species being only strongly marked and fixed varieties, we might surely expect to find them still often continuing to vary in those parts of their structure which have varied within a moderately recent period, and which have thus come to differ. Or to state the case in another manner: the points in which all the species of a genus resemble each other, and in which they differ from the species of some other genus, are called generic characters; and these characters in common I attribute to inheritance from a common progenitor, for it can rarely have happened that natural selection will have modified several species, fitted to more or less widely-different habits, in exactly the same manner: and as these so-called generic characters have been inherited from a remote period, since that period when the species first branched off from their common progenitor, and subsequently have not varied or come to differ in any degree, or only in a slight degree, it is not probable that they should vary at the present day. On the other hand, the points in which species differ from other species of the same genus, are called specific characters; and as these specific characters have varied and come to differ within the period of the branching off of the species from a common progenitor, it is probable that they should still often be in some degree variable, at least more variable than those parts of the organisation which have for a very long period remained constant.In connexion with the present subject, I will make only two other remarks. I think it will be admitted, without my entering on details, that secondary sexual characters are very variable; I think it also will be admitted that species of the same group differ from each other more widely in their secondary sexual characters, than in other parts of their organisation; compare, for instance, the amount of difference between the males of gallinaceous birds, in which secondary sexual characters are strongly displayed, with the amount of difference between their females; and the truth of this proposition will be granted. The cause of the original variability of secondary sexual characters is not manifest; but we can see why these characters should not have been rendered as constant and uniform as other parts of the organisation; for secondary sexual characters have been accumulated by sexual selection, which is less rigid in its action than ordinary selection, as it does not entail death, but only gives fewer offspring to the less favoured males. Whatever the cause may be of the variability of secondary sexual characters, as they are highly variable, sexual selection will have had a wide scope for action, and may thus readily have succeeded in giving to the species of the same group a greater amount of difference in their sexual characters, than in other parts of their structure.It is a remarkable fact, that the secondary sexual differences between the two sexes of the same species are generally displayed in the very same parts of the organisation in which the different species of the same genus differ from each other. Of this fact I will give in illustration two instances, the first which happen to stand on my list; and as the differences in these cases are of a very unusual nature, the relation can hardly be accidental. The same number of joints in the tarsi is a character generally common to very large groups of beetles, but in the Engidae, as Westwood has remarked, the number varies greatly; and the number likewise differs in the two sexes of the same species: again in fossorial hymenoptera, the manner of neuration of the wings is a character of the highest importance, because common to large groups; but in certain genera the neuration differs in the different species, and likewise in the two sexes of the same species. This relation has a clear meaning on my view of the subject: I look at all the species of the same genus as having as certainly descended from the same progenitor, as have the two sexes of any one of the species. Consequently, whatever part of the structure of the common progenitor, or of its early descendants, became variable; variations of this part would it is highly probable, be taken advantage of by natural and sexual selection, in order to fit the several species to their several places in the economy of nature, and likewise to fit the two sexes of the same species to each other, or to fit the males and females to different habits of life, or the males to struggle with other males for the possession of the females.Finally, then, I conclude that the greater variability of specific characters, or those which distinguish species from species, than of generic characters, or those which the species possess in common; that the frequent extreme variability of any part which is developed in a species in an extraordinary manner in comparison with the same part in its congeners; and the not great degree of variability in a part, however extraordinarily it may be developed, if it be common to a whole group of species; that the great variability of secondary sexual characters, and the great amount of difference in these same characters between closely allied species; that secondary sexual and ordinary specific differences are generally displayed in the same parts of the organisation, are all principles closely connected together. All being mainly due to the species of the same group having descended from a common progenitor, from whom they have inherited much in common, to parts which have recently and largely varied being more likely still to go on varying than parts which have long been inherited and have not varied, to natural selection having more or less completely, according to the lapse of time, overmastered the tendency to reversion and to further variability, to sexual selection being less rigid than ordinary selection, and to variations in the same parts having been accumulated by natural and sexual selection, and thus adapted for secondary sexual, and for ordinary specific purposes.Distinct species present analogous variations; and a variety of one species often assumes some of the characters of an allied species, or reverts to some of the characters of an early progenitor.
3. 据上游新闻·重庆晨报报道,有资深影院人士透露,应该还会有春节档电影宣布提档,而提档的原因很可能是因为《唐人街探案3》预售的遥遥领先。
4. 宣宗时,全国商业城市约有三十多座(《宣宗实录》卷五十)。各城市之间,由商路连接,形成商业市场的网络。商品运输的交通工具主要是车船。永乐时边境用兵,使用大型的马拉运输工具“武纲车”运粮。民间有四轮大马车,用来进行长途运输。陆路运输有小型马、牛车,人力独轮车。船是南方重要的运输工具。漕船是平底浅船,“载米可近二千石”(《天工开物》卷中)。明初沿用元代的“遮洋浅船”或“钻风船”在近海航行,运粮辽东。
5.   "I then gave him some more; three times did I fill the bowl for him,and three times did he drain it without thought or heed; then, whenI saw that the wine had got into his head, I said to him asplausibly as I could: 'Cyclops, you ask my name and I will tell ityou; give me, therefore, the present you promised me; my name isNoman; this is what my father and mother and my friends have alwayscalled me.'
6. 其实,中学是人成长至为重要的阶段,中学课堂上要克服长期以来存在的填鸭式教学、培养学生的批判性思维能力,课堂上启发式教学、指导学生进行研究型作业不可或缺。

时尚

1. 但是,这种药只是有动物试验的结果,后续还需要经过人体三期临床试验,如果成功,才能获得美国食品与药物管理局(FDA)的批准。
2. 阿森纳队
3.   When the bright star that heralds the approach of dawn began toshow. the ship drew near to land. Now there is in Ithaca a haven ofthe old merman Phorcys, which lies between two points that break theline of the sea and shut the harbour in. These shelter it from thestorms of wind and sea that rage outside, so that, when once withinit, a ship may lie without being even moored. At the head of thisharbour there is a large olive tree, and at no distance a fineoverarching cavern sacred to the nymphs who are called Naiads. Thereare mixing-bowls within it and wine-jars of stone, and the bees hivethere. Moreover, there are great looms of stone on which the nymphsweave their robes of sea purple- very curious to see- and at all timesthere is water within it. It has two entrances, one facing North bywhich mortals can go down into the cave, while the other comes fromthe South and is more mysterious; mortals cannot possibly get in byit, it is the way taken by the gods.
4. 印度的Risug需要医生将药物注射进男性体内新型避孕药全面开花这种女性月服避孕药的最大优势是长效,相当于一些药物的缓释胶囊,胶囊大小与普通鱼油片剂相同。
5. 所以与其纠结是不是开门迎客,夫妻俩开始学习《疫情之下餐饮企业的应对方案》,这是一门向餐饮人免费开放的在线教学课程,比如优化流程避免交叉感染、做好堂食与外卖把控食品安全、降低用工成本、人员留存、特殊时期工资如何发放……同时,他们也与很多从事餐饮的头部企业交流,发现很多大企业也有向小而美转向的打算。
6. 近日,一位13岁花季少女吞药自杀后在重症监护室抢救的消息,让人莫名心疼。

推荐功能

1. 因此,在这里贷出的资本,决不是闲置的资本,而是在它的所有者手中必须变更自己形式的资本,是对它的所有者来说只是存在于商品资本形式上的资本,也就是必须完成再转化,即至少必须先转化为货币的资本。可见,在这里,信用是商品形态变化的媒介,即不仅是W—G,而且也是G—W和现实生产过程的媒介。把银行家的信用撇开不说,再生产循环内大量的信用,并不意味着有大量闲置资本打算贷出和寻找有利的投资场所,而是表明资本在再生产过程内已被大量动用。所以,信用的中介作用在这里表现为:1.就产业资本家来说,使产业资本由一个阶段转移到另一个阶段,使彼此有关和彼此衔接的各生产部门联系起来;2.就商人来说,使商品由一个人手里运到和转入另一个人手里,直到商品最终出售,变成货币,或者交换成其他商品。
2.   "Let there be no mistake, vizir," said the Sultan. "Remember you will have to take her life yourself. If you refuse, I swear that your head shall pay forfeit."
3. 记者在上海链家多家门店获悉,链家经纪人在各渠道发布的房源均须是满足真实存在、真实在售、真实价格、真实图片4个标准的真房源。
4.   Previous Chapter
5.   Faust. Mephistopheles
6. 其中,一英寸版本由Insta360与徕卡联合设计。

应用

1.   Now, it came to passe (within no long while after) that Fortunebeing favourable to our injured Scholler, prepared a new accident,wherby he might fully effect his harts desire. For the lusty yongGallant, who was Madame Helenaes deare darling and delight, and (forwhose sake) she dealt so inhumanely with poore Reniero: became wearyof her amourous service, and was falne in liking of another Lady,scorning and disdaining his former Mistresse; whereat shee grewexceedingly displeased, and began to languish in sighes and teares.
2.   Dear Watson:
3. “人们已习惯于这样的套路:美联储称要进行紧缩,结果当市场波动或其他风险浮出水面时,政策制定者便收回紧缩言论,呈现出‘如有疑问,按兵不动’的规律,”克普克说。
4. 最早的惩罚措施,是禁止被定罪的垄断者使用公共设施,包括邮政服务和铁路运输服务。后来又有人提出禁止垄断者使用联邦法庭,结果这些做法被发现行不通,便开始要垄断者发配充军,参与在欧洲爆发的战事。实施一段时间后,有议员又建议让涉嫌垄断者多交税,但这无异于认同了垄断行为,还是行不通;后来才逐渐出现强行分拆公司和干预产品内部设计等措施。
5.   `Not at all,' said Dukes; `the top of you's by no means hors de combat. You've got the life of the mind sound and intact. So let us hear your ideas.'
6. "I'll tell you what, Sara," she said. "Pretend you are a princess now and this is a royal feast."

旧版特色

1. "It is true that the first thought was mine, Sahib," he said; "though it was naught but a fancy. I am fond of this child; we are both lonely. It is her way to relate her visions to her secret friends. Being sad one night, I lay close to the open skylight and listened. The vision she related told what this miserable room might be if it had comforts in it. She seemed to see it as she talked, and she grew cheered and warmed as she spoke. Then she came to this fancy; and the next day, the Sahib being ill and wretched, I told him of the thing to amuse him. It seemed then but a dream, but it pleased the Sahib. To hear of the child's doings gave him entertainment. He became interested in her and asked questions. At last he began to please himself with the thought of making her visions real things."
2. 其实早在上世纪八十年代,硅谷就流行起了在家办公的SOHO模式,在IBM、微软、Google、Facebook等科技公司中颇为流行,云数据中心公司哈希有85%的员工在其他地方,开源软件平台GitLab称自己是一家纯远程办公公司。
3. vt. 把 ...

网友评论(84855 / 18129 )

  • 1:孙旺泉 2020-07-17 19:48:38

    翻船后多人抓扶已被淹没的船舶。

  • 2:邓小刚 2020-08-05 19:48:38

    谷歌是另一种做法,它的形象,它代表的东西。

  • 3:祝达令 2020-08-02 19:48:38

      `Connie, this is the new game-keeper, Mellors. You haven't spoken to her ladyship yet, Mellors?'

  • 4:李田友 2020-07-19 19:48:38

      22. His brother: Hector.

  • 5:欧巴桑 2020-07-31 19:48:38

    山东战场上,一三五九年七月间,毛贵部下续继祖等自辽阳至益都,杀赵均用。两军部下自相仇杀。毛贵、赵均用死后,农民军各部陷于混乱。一三六○年,只有田丰和王士诚等部仍在继续进攻。三月,田丰军攻下保定路。四月,元朝派使臣至田丰军谕降,田丰斩使拒降。王士诚部转战晋冀,七月间被孛罗帖木儿军击败,走依田丰。田丰、王士诚等据东平,指挥各部。一三六一年六月,察罕帖木儿进兵山东,发山西及汴梁军两路并进。八月,察罕帖木儿养子扩廓帖木儿(汉人,原名王保保)等由东阿造浮桥渡河,田丰部二万人夺桥抱战,失败。察罕帖木儿部关保等渡河攻占长清,至东平。田丰战败投降。王士诚及棣州俞宝、东昌杨诚等部农民军相继投降。察罕帖木儿进兵济南,攻围三月,农民军济南守将刘珪降元。山东地区全被元军夺去。只有益都一城,仍由农民军陈猱头部拒守,声援安丰的大宋。

  • 6:邬大光 2020-07-24 19:48:38

    之后,他又联系了金银潭医院,他们那边有部队来支援的医生,我想部队上的人一般都自己理发,想跟他们借理发工具,但人家说已经转到火神山医院了。

  • 7:李昆鹏 2020-08-05 19:48:38

    当时全场小学音乐教师都觉得说的很实在,自发鼓掌两次。

  • 8:程双喜 2020-07-25 19:48:38

      "And then if that little real estate deal I've got on goesthrough, we'll get married," he said with a great show ofearnestness, the while he took his place before the mirror andbegan brushing his hair.

  • 9:秦亚洲 2020-07-20 19:48:38

      "Both of your lamps were lit, of course?"

  • 10:肯尼迪 2020-07-29 19:48:38

      'I don't dislike you, Miss: I believe I am fonder of you than ofall the others.'

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