The young brachiopod now attaches itself its lower segment E, and the middle segment increases greatly in size, as form a kind hood need to write an argumentative essay enclosing the front segment in part Then the front segment F, G decreases in size the middle portion originates the bivalve shell which soon comes enclose the marketing writer body H, the lower or third segment being represented the disc or stalk attachment The technicality the subject prevents our following out for the reader the later stages lampshell growth, in which striking likenesses are presented, not merely brachiopods now extinct, but likewise groups plant-like animals, named Polyzoa 1, 1, and which the Sea-mats Flustrd our coasts are good examples. Hence conclude that the brachiopods present with a group which has sprung from a worm-like stock, along with the sea-mats, thus showing tlie possibility higher molluscs having had a similar origin.
The early history the worms themselves forms a concluding phase in these investigations into the history the moUuscan race. If study the development one the true shall find a striking reproduction some features with which our molluscan researches have already made familiar.
The young worm makes its first appearance as an active freeswimming barrel-sh nped body, provided with cilia, disposed in rious fashions, in different groups the class.
Thus, in some em bryos B, C there a first band cilia around the body in front exists at the opposite extremity, and tufts these cilia website that writes your essays for you may also developed at the extreme front IS provided with cilia, disposed chiefly in two rings, one at either In some Byeways Development.
1 extremity the body. Soon tentacles are developed from the head portion, the body becomes segmented, and the tentacle which, under the name Operailum iO destined form a stopper the mouth the tube, may likewise discerned. At this stage, with its segmented body, the young tube-dwelling worm resembles the pennanent condition help with scholarship essays its free-hving neighbour the sand. Hence, when discover that the tube-dweller finally secretes a tube, and lodges its body therein, becoming a stationary form, conclude, rationally enough, that both kinds worms have arisen from one common stock, and that the tube-dwellers represent the more modified race the two groups whilst they dissertation review likewise may regarded as degraded forms when compared with their freeliving neighbours. extending from those the molluscs, through the lampshells, and finally best custom essay sites ending with that the worms themselves.
Is there evidence at hand show that something more than a theoretical conception the connection between these apparently dissimilar forms answer such a question depends the credence place what development teaches. If the truth repeats descent not admitted, worsethan useless invite comparison between the larva a chiton and that a worm. Unless the mind has been prepared discover in development the shitting and progressive past history a species, there can no benefit, an intellectual kind in comparing the likeness the young brachiopod with the early stages the worm.
But, buy essays cheap conversely, when admitted that all development meaningless unless some idea its use, purport, or cause afforded, and when in the study the phases an animal's growth are led see prospects tracing its past evolution, the likenesses and analogies development become forcibly plain and valuable.
Primarily, may said, a very large part the reasonableness evolution depends its rational interpretations development. Without development and its lessons, evolution would well-nigh unprovable. Conversely, without the idea evolution, the development animal or plant a meaningless piece natural transmogrification and change.
In far as the life-histories at which have just glanced are concerned, the general conclusions drawn from their study lie the surface the subject. Beginning with the worms and their transformations, find a type larva, presenting a rounded body with variously disposed cilia, which simply becomes segmented, and with little further change becomes the worm. From the worms the Lampshells an easy transition, for in the development the latter find the clearest reproduction the features the young worm larva in write my paper co the body divided into its three segments and exhibiting its cilia and eye-spots whilst, as Huxley remarks, the resemblance the worm-larva increased when find the young lampshell developing bundles bristles 1, F, G, such as the worm possesses, the middle joint its body. From such resemblances, Huxley more than justified in remarking that, whilst the lampshells bear a likeness in development the plant-like Sea-mats and their neighbours 1, I, their development no less strongly testifies their close relations with the worms. Thus the evolution a race lower shellfish from a worm-stock plainly enough taught development and such a fact testifies directly enough the possibilities other molluscan developments having had a similar origin. Coming next in order the molluscs themselves, find two classes the bivalves and the gasteropods in each which buy essay cheap certain primitive forms development may traced. The Veliger stnge, A may regarded as common both groups and the common origin for both classes may reasonably enough argued for and maintained this ground alone, and apart from any plain agreement in stnicture.
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