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OriginOfSpecies - 475 Rows
Column Type #Values Column Stats
id int(11) 475 Column Stats
subject varchar(80) 14 Column Stats
title varchar(250) 139 Column Stats
ordinal int(11) 30 Column Stats
description text 474 Column Stats

475 rows, page 61 of 119 (4/p)
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Export to Excel select * from OriginOfSpecies order by subject limit 240, 4 (Page 61: Row)
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05 - Laws of Variation 05-04 - Correlation of Growth 50 With respect to the development of the corolla, Sprengel's idea that the ray-florets serve to attract insects, whose agency is highly advantageous or necessary for the fertilisation of these plants, is highly probable; and if so, natural selection may have come into play.

But with respect to the seeds, it seems impossible that their differences in shape, which are not always correlated with any difference in the corolla, can be in any way beneficial: yet in the Umbelliferae these differences are of such apparent importance- the seeds being sometimes orthospermous in the exterior flowers and coelospermous in the central flowers,- that the elder De Candolle founded his main divisions in the order on such characters.

umbelliferae
umbelliferae

Alphonse de Candolle
Alphonse de Candolle


Hence modifications of structure, viewed by systematists as of high value, may be wholly due to the laws of variation and correlation, without being, as far as we can judge, of the slightest service to the species.
05 - Laws of Variation 05-08 - Parts Developed in an Unusual Manner are Highly Variable 10 A Part developed in any Species in an extraordinary degree or manner, in comparison with the same Part in allied Species, tends to be highly variable.
05 - Laws of Variation 05-08 - Parts Developed in an Unusual Manner are Highly Variable 20 Several years ago I was much struck by a remark, to the above effect, made by Mr. Waterhouse.
George Robert Waterhouse
George Robert Waterhouse


Professor Owen, also, seems to have come to a nearly similar conclusion.
Richard Owen
Richard Owen


It is hopeless to attempt to convince any one of the truth of the above proposition without giving the long array of facts which I have collected, and which cannot possibly be here introduced.

I can only state my conviction that it is a rule of high generality. I am aware of several causes of error, but I hope that I have made due allowance for them. It should be understood that the rule by no means applies to any part, however unusually developed, unless it be unusually developed in one species or in a few species in comparison with the same part in many closely allied species.

Thus, the wing of a bat is a most abnormal structure in the class of mammals, but the rule would not apply here, because the whole group of bats possesses wings; it would apply only if some one species had wings developed in a remarkable manner in comparison with the other species of the same genus.

bat
bat


The rule applies very strongly in the case of secondary sexual characters, when displayed in any unusual manner.

The term, secondary sexual characters, used by Hunter, relates to characters which are attached to one sex, but are not directly connected with the act of reproduction.

The rule applies to males and females; but more rarely to the females, as they seldom offer remarkable secondary sexual characters.

The rule being so plainly applicable in the case of secondary sexual characters, may be due to the great variability of these characters, whether or not displayed in any unusual manner- of which fact I think there can be little doubt.

But that our rule is not confined to secondary sexual characters is clearly shown in the case of hermaphrodite cirripedes; I particularly attended to Mr. Waterhouse's remark, whilst investigating this Order, and I am fully convinced that the rule almost always holds good.
cirripede
cirripede


I shall, in a future work, give a list of all the more remarkable cases; I will here give only one, as it illustrates the rule in its largest application.

The opereular valves of sessile cirripedes (rock barnacles) are, in every sense of the word, very important structures, and they differ extremely little even in distinct genera; but in the several species of one genus, Pyrgoma, these valves present a marvelous amount of diversification; the homologous valves in the different species being sometimes wholly unlike in shape; and the amount of variation in the individuals of the same species is so great, that it is no exaggeration to state that the varieties of the same species differ more from each other in the characters derived from these important organs, than do the species belonging to other distinct genera.
05 - Laws of Variation 05-08 - Parts Developed in an Unusual Manner are Highly Variable 30 As with birds the individuals of the same species, inhabiting the same country, vary extremely little, I have particularly attended to them; and the rule certainly seems to hold good in this class.

bird
bird


I cannot make out that it applies to plants, and this would have seriously shaken my belief in its truth, had not the great variability in plants made it particularly difficult to compare their relative degrees of variability.