At the end of the Devonian period (), the seas, rivers and lakes were teeming with life but the land was the realm of early plants and devoid of vertebrates though some, such as Ichthyostega, may have sometimes hauled themselves out of the water.

The integumentary structure contains some typical characteristics common to terrestrial vertebrates, such as the presence of highly cornified outer layers, renewed periodically through a moulting process controlled by the pituitary and thyroid glands.

The brain is small and simple in some species, such as nematode worms ; in other species, including vertebrates, it is the most complex organ in the body.

The groups considered to have a good fossil record, including a number of transitional fossils between traditional groups, are the vertebrates, the echinoderms, the brachiopods and some groups of arthropods.

Hemoglobin (; also spelled haemoglobin and abbreviated Hb or Hgb ) is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates ( with the exception of the fish family Channichthyidae ) as well as the tissues of some invertebrates.

The division of the entire Kingdom Animalia into vertebrates ( about 40000 species in part of one phylum ) and invertebrates certainly is convenient in some practical contexts, but to put it into taxonomic perspective, it is roughly on the same scale as dividing the animal kingdom into Gastropoda ( perhaps 60000 species in part of one phylum ) and non-Gastropoda ; worthwhile only in certain constrained contexts.

It's also possible that some humans believe that, they themselves being vertebrates, the group deserves more attention than invertebrates.

In addition, some species included are only remotely related to one another, with some more related to vertebrates than other invertebrates.

For example, introns are extremely common within the nuclear genome of higher vertebrates ( e. g. humans and mice ), where protein-coding genes almost always contain multiple introns, while introns are rare within the nuclear genes of some eukaryotic microorganisms, for example baker's / brewer's yeast ( Saccharomyces cerevisiae ).

The kidneys are organs that serve several essential regulatory roles in most animals, including vertebrates and some invertebrates.

Myelin is considered a defining characteristic of the ( gnathostome ) vertebrates, but myelin-like sheaths have also arisen by parallel evolution in some invertebrates, although they are quite different from vertebrate myelin at the molecular level.

In vertebrates, the majority of neurons belong to the central nervous system, but some reside in peripheral ganglia, and many sensory neurons are situated in sensory organs such as the retina and cochlea.

Estrogens are synthesized in all vertebrates as well as some insects.

Fossils suggest they may have possessed many modern attributes even by the late Carboniferous, and it is possible that they captured small vertebrates, for some species had a wing span of 71 cm.

However, the hearts of some other arthropods ( including spiders and crustaceans such as crabs and shrimp ) and some other animals pump hemolymph, which contains the copper-based protein hemocyanin as an oxygen transporter similar to the iron-based hemoglobin in red blood cells found in vertebrates.

The stomach is a muscular, hollow, dilated part of the digestion system which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects ( mid-gut ), and molluscs.

Moreover, some analyses do not regard Conodonts as either vertebrates or craniates, because they lack the main characteristics of these groups.

There are studies using warm-blooded vertebrates and humans in vivo, with some suggesting that they recover more rapidly from infections or critical illness due to fever.

Trogons feed principally on insects, other arthropods, and fruit ; to a lesser extent some small vertebrates such as lizards are taken.

In some lower vertebrates, ( e. g. the pigeon ) there is a " centrifugal " control of messages-that is, one layer can control another, or higher regions of the brain can drive the retinal nerve cells, but in primates this does not occur.

As jellyfish are not even vertebrates, let alone true fish, the usual word jellyfish is considered by some to be a misnomer, and American public aquariums have popularized use of the terms jellies or sea jellies instead.

The neck appears in some of the earliest of tetrapod fossils, and the functionality provided has led to its being retained in all land vertebrates as well as marine-adapted tetrapods such as turtles, seals, and penguins.

When it comes to this, I shall prefer emigrating to some country where they make no pretence of loving liberty -- to Russia, for instance, where despotism can be taken pure, without the base alloy of hypocrisy '' ( His emphasis )

Underlying these conceptions of mimesis are certain presuppositions concerning the nature of primary human experience which require some exposition before the main argument can proceed.

We feel uncomfortable at being bossed by a corporation or a union or a television set, but until we have some knowledge about these phenomena and what they are doing to us, we can hardly learn to control them.

`` I've been in government and I can tell some pretty hairy stories about personnel difficulties, so I know what a problem he was ''.

We must avoid the notion, suggested to some people by examples such as those just mentioned, that ideas are `` units '' in some way comparable to coins or counters that can be passed intact from one group of people to another or even, for that matter, from one individual to another.

Now omitting for a moment some recent developments we can say the Saxon Shore hypothesis of Lappenberg and Kemble has undergone virtual eclipse in this century.

In some instances a seventh question can be added: 7.

The demand for these lots can be met for some time to come.

I was surprised at Mayor Miriani's defeat, but perhaps Mayor-elect Cavanagh can accomplish some things that should have been done years ago.

Maybe he can clean out the white elephants in some of the city departments such as welfare, DPW and sanitation.

How can we old-fashioned parents, who still feel that adults are due some respect from children, battle the new type of advertising that appears on TV without denying the children the use of television entirely??

I suppose I am missing some elementary point but I honestly cannot see how two wrongs can make a right!!

There is even some question whether the U.S. can any longer defend itself against an initiative by the Left.

I know of no other solution than the one N.C. proposes -- to do what we can for each sufferer as he confronts us, hoping that this will spread beyond him to others at some time and some place.

More than that, Sam Rayburn is the very living symbol of an iron-clad integrity so powerful in his nature and so constantly demonstrated that he can count some of his best friends in the opposition.

Steps should also be taken to link the Food for Peace Program with the Peace Corps, so that foreign currencies accumulated by the sale of U.S. surplus food under P.L. 480 can be put to use to pay some of the host country expenses of Peace Corps personnel.

Since broadcast frequencies are very limited in number, these objectives are to some extent inconsistent in that not all of them can be fully realized, and to the extent that each is realized, there is a corresponding reduction of the possibilities for fullest achievement of the others.

Therefore, under our longstanding allocation rules, on some of these channels no station other than the dominant ( class 1 ) -- A ) station is permitted to operate at night, so that the 1, -- A station can render service, interference free, wherever it can be received.

It is more than just lack of dance training that is our problem, for just as gymnastics can learn from dance, dance has some very important things to learn from gymnastics.

Sonar can be used to measure the thickness of the heart by placing small crystal transducers at opposite sides of the heart or blood vessel and exciting one with some pulsed ultrasonic energy.

Will your trade customers settle for less attention and fewer frills in return for some benefit they can share??

and translate the whole into profit and loss and balance sheet figures which management can act on with some assurance??