Word Finder - morphological

definition

Of, or pertaining to, morphology.

This has had a most important effect on the development in recent years of morphological anatomy.

The standing of the Trichoptera in a position almost ancestral to the Lepidoptera is one of the assured results of recent morphological study, the mobile mandibulate pupa and the imperfectly suctorial maxillae of the Trichoptera reappearing in the lowest families of the Lepidoptera.

Considering the wide differences between the two groups in the size and external characters, and in the mode of life, including the mode of feeding, it is indeed surprising that in every important organ the two groups should show a fundamental morphological identity.

At the present time some objection is being taken to this purely morphological conception of the body and its parts as being too abstract.

Divergent views have been held as to the morphological significance of the pneumatophore.

Under the vague term " double " many very different morphological changes are included.

Rosenkranz, who in his work Hegel's Naturphilosophie seeks to develop Hegel's idea of an earthorganism in the light of modern science, recognizing in crystallization the morphological element.

Evolution, or development, is, in fact, at present employed in biology as a general name for the history of the steps by which any living being has acquired the morphological and the physiological characters which distinguish it.

Theoretically this branch of the subject should connect with and form the completion of morphological anatomy, but the field, has not yet been sufficiently explored to allow of the necessary synthesis.

The pursuit of this study has not only thrown valuable light on the economy of the plant as a whole, but forms an indispensable condition of the advance of morphological anatomy.

Notwithstanding the fact, however, that these cells are capable of acting as very efficient lenses the explanation given by Haberlandt has not been widely accepted and evidence both morphological and physiological has been brought forward against it.

When two organs can be traced along the same line of descent to one primitive form, that is when they are found to be mono phyletic, their homology is complete; when, however, they are traceable to two primitive forms, though these forms belong to the same morphological series, they are polyphyletic and therefore only incompletely homologous.

All organs performing the same function and showing similar adaptations are said to be analogous or homoplastic, whatever their morphological nature may be; hence organs are sometimes both homologous and analogous, sometimes only analogous.

These changes may be brought about by external causes, such as the attacks of insects or of fungi, alterations in external conditions, &c., or by some unexplained internal disturbance of the morphological equilibrium.

Useful and suggestive as they often are, teratological facts played, at one time, too large a part in the framing of morphological theories; for it was thought that the monstrous form gave a clue to the essential nature of the organ assuming it.

AdaptationThe morphological and physiological differentiation of the plant-body has, so far, been attributed to (I) the nature of the organism, that is to its inherent tendency towards higher organization, and (2) to the indefinite results of the external conditions acting as a stimulus which excites the organism to variation, but does not direct the course of variation.

Moreover, had the evolution of plants proceeded along the line of adaptation, the vegetable kingdom could not be subdivided, as it is, into the morphological groups Thallophyta, Bryophyta, Pteridophyta, Phanerogamia, but only into physiological groups, Xerophyta, Hygrophyta, Tropophyta, &c.

Sachs was the first to formulate the theory that morphological differences are the expression of differences in material composition.

The two conceptions which may now be said to animate the theory of geography are the genetic, which depends upon processes of origin, and the morphological, which depends on facts of form and distribution.

It is to be noted that often no absolute line of demarcation can be drawn in regard to these regions, their definitions being rather convenient than morphological.

The results are as interesting from a morphological point of view (showing the subtle and gradual modifications of these organs in their various adaptations), as they are sparse in taxonomic value, far less satisfactory than are those of the hind-limb.

Goodrich, endorsed by Lankester, led to the opinion that under the general morphological conception of "nephridium" were included two distinct sets of organs, viz.

It is possible, however, that those oviducts belong to a separate morphological category, more comparable to the dorsal pores and to abdominal pores in some fishes.

In the Eudrilidae there are spermathecae of different morphological value.

The vascular system does not readily lend itself to morphological comparison between such widely different animals as Balanoglossus and Amphioxus, and the reader is therefore referred to the memoirs cited at the end of this article for further details.

Between the two and at the highest point of the arc, so far as morphological differentiation is concerned, stands the scorpion; near to it in the trilobite's direction (that is, on the ascending side) are Limulus and the Eurypterines - with a long gap, due to obliteration of the record, separating them from the trilobite.

Cuvier's doctrine of four plans of structure was essentially a morphological one, and so was the single-scale doctrine of Buffon and Lamarck, to which it was opposed.

Cuvier's morphological doctikne received its fullest development in the principle of the " correlation of parts," which he applied to palaeontological investigation, namely, that every animal is a definite whole, and that no part can be varied without entailing correlated and law-abiding variations in other parts, so that from a fragment it should be possible, had we a full knowledge of the laws of animal structure or morphology, to reconstruct the whole.

Owen not only occupied himself with the dissection of rare animals, such as the Pearly Nautilus, Lingula, Limulus, Protopterus, Apteryx, &c., and with the description and reconstruction of extinct reptiles, birds and mammals - following the Cuvierian tradition - but gave precision and currency to the morphological doctrines which had taken their rise in the beginning of the century by the introduction of two terms, " homology " and " analogy," which were defined so as to express two different kinds of agreement in animal structures, which, owing to the want of such " counters of thought," had been hitherto continually confused.

His true greatness can only be estimated by a consideration of the fact that he was a great teacher not only of human and comparative anatomy and zoology but also of physiology, and that nearly all the most distinguished German zoologists and physiologists of the period 1850 to 1870 were his pupils and acknowledged his leadership. The most striking feature about Johann Miller's work, apart from the comprehensiveness of his point of view, in which he added to the anatomical and morphological ideas of Cuvier a consideration of physiology, embryology and microscopic structure, was the extraordinary accuracy, facility and completeness of his recorded observations.

In arranging plants according to a natural method, we require to have a thorough knowledge of structural and morphological botany, and hence we find that the advances made in these departments have materially aided the efforts of systematic botanists.

This gives rise to the great morphological difference, that in the former regions, the Astin-tagh and the Kuruk-tagh, the products of disintegration are almost always carried away by the wind, and so disappear; no matter how powerful or how active the disintegration may be, none of the loosened material ever succeeds either in gathering amongst the mountains or in accumulating at their foot.

But though the great morphological features of this latitudinal valley forcibly recall the latitudinal valleys of Tibet, the climatic differences give rise to differences between the basins corresponding to the differences between the mountain-ranges themselves.

In external form and appearance the Hydrozoa exhibit such striking differences that there would seem at first sight to be little in common between the more divergent members of the group. Nevertheless there is no other class in the animal kingdom with better marked characteristics, or with more uniform morphological peculiarities underlying the utmost diversity of superficial characters.

The sense-organs are always situated at the margin of the unbrella and may be distinguished from the morphological point of view into two categories, according as they are, or are not, derived from modifications of tentacles; in the former case they are termed tentaculocysts.

This is apparently owing to the facts that too much has been attempted in the definition, and that differences arise according as we aim at a morphological or a physiological definition.

On this basis, with other interesting morphological comparisons, Brefeld erected his hypothesis, now untenable, that the Ascomycetes and Basidiomycetes diverge from the Zygomycetes, the former having particularly specialized the ascus (sporangial) mode of reproduction, the latter having specialized the conidial (indehiscent one-spored sporangiole) mode.

In the last-named family the single morphological species Erysiphe graminis is found growing on the cereals, barley, oat, wheat, rye and a number of wild grasses (such as Poa, Bromus, Dactylis).

The vast advance in knowledge of the existing forms of living things that has been acquired and recorded since 1859 has accentuated the difficulty of finding any morphological criteria for species.

Investigation has shown that many other parts of a plant which externally appear very different from ordinary leaves are, in their essential particulars, very similar to them, and are in fact their morphological equivalents.

All modifications of leaves follow the same laws of arrangement as true leaves - a fact which is of importance in a morphological point of view.

Parker observes of their brain capacity and is an additional testimony to their low morphological rank.

But the great diversity of these abnormal cases as shown in the examples cited above suggests the use of great caution in formulating definite morphological theories upon them.

The similarity of the morphological characters of one group of fungi to those of certain algae has earned for it the name of Phycomycetes or alga -fungi.

Notwithstanding the absence of chlorophyll, and the consequent parasitic or saprophytic habit, Bacteriaceae agree in so many morphological features with Cyanophyceae that the affinity can hardly be doubted.

Altogether it is difficult on morphological grounds to resist the conclusion that Florideae present the same fundamental phenomenon of alternation of generations as prevails in the higher plants.

The presence of phycocyanin, phyco a role in the morphological development of land plants is entirely wanting in algae, such conducting tissues as do exist in the larger Phaeophyceae and Rhodophyceae serving rather for the convection of elaborated organic substance, and being thus comparable with the phloem of the higher plants.

Thus Goethe had no great sympathy for the war of liberation which kindled young hearts from one end of Germany to the other; and when the national enthusiasm rose to its highest pitch he buried himself in those optical and morphological studies, which, with increasing years, occupied more and more of his time and interest.

The renal organs of the oyster were discovered by Hoek to agree in their morphological relations with those of other lamellibranchs.

Tubers are also sometimes formed on aerial branches, as in some Aroids, Begonias, &c. The production of small green tubers on the haulm, in the axils of the leaves of the potato, is not very unfrequent, and affords an interesting proof of the true morphological nature of the underground shoots and tubers.