Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/711

Rh member only of which, Peneus, has a stage been detected. The and the  possess alike three pairs of, and three for ingestion of food. The in both is without appendages, and the  are without. Admitting the resemblances, there is a prior question to be settled in the case of, , and. Are the temporary nal investments of these s, the ular and the structureless s, to be compared with the blastodermic s of, with that whose presence in the  is accepted by some observers, as the last trace of the  stage? In the  found the inner layer to invest the  after the outer gave way, and  recognises the deutovum in Platygaster also. The identification with the is strongly denied by the last-named observer; but there is still room for further investigation, since logists of high reputation differ so entirely on the matter of fact, irrespective of phylogenetic theories. Should the identification be accepted, the Arthropods would, as a group, argree in having a stage, different in detail in each ; the second, or  stage, would differ still more in each, and the homologies of the parts would thus become obscured in details, the identity of the general plan being clearly recognisable. All the Arthropods agree in having the terminal portion of the derived from the outer, the middle portion from the inner nic layer. Lastly, the Arthropods, in common with the and, have their body-cavity, or perivisceral space, formed by the splitting of the mesoblast, or derivative layer formed between the outer and inner layer (epiblast and hypoblast, and ectoderm and endoderm). In, in the higher , and , segmentation is partial; in , and the lower , and , it is total; but as in , for example, the unsegmented  undergoes at a later period a division into polygonal masses, the difference, though of value in classification, is not of primary importance. The relation of the branchiate Arthropods, the, to the other three te es, has been discussed chiefly from a phylogenetic point of view. The priority of aquatic to terrestrial forms is assumed, and the derivation of the latter from the former is traced in various ways. The or  of the Arthropod retain, more than the nervous system which is derived from the epiblast, and still more than the alimentary canal and its appendages, the annulose characteristic that each represents a unit; each may, and many do, give rise to appendages originally similar, but afterwards modified for special functions. Hence the same limbs are in,  in ,  in some ,  in others,  in some,  in others. In the  of the adult is destitute of appendages, but many  are provided with l s, that is, external processes in which air-canals ramify, and in which a large quantity of blood is received within the cavity of the thin-walled dilatable process. These processes are destitute of external apertures, the l system is in them closed. Such structures are found but rarely to co-exist with the open condition of this l system. But , one of the Orthopterous, is remarkable for this conjunction, the branchial processes of the adult overhanging the of the. Considerable variety exists in the position of the s. The of  have three  pairs of s, and are terminal of the. In other cases they are confined to the. Now, it is to be noted that these projections are not at first l; in Chloea the  appear after another, and they are then vibratile. Further, they are developed from the upper surface of the body. Now, in the the limbs are typically double pairs projected from the sides of the body; the  consist of two branches, notopodium and neuropodium, and the s when present are modifications of the notopodium. In the this bipartite condition is indicated by the exopodial and endopodial divisions of the limbs. In the adult this duplicity has disappeared, unless we recognise in the position of the   the equivalent of the branchiferous notopodium. and regard the s as l s transferred from  to. thinks that the dropping off of the s determines the opening of the l system by the or s. Further, he assigns to the closed l system a function similar to that of the  of es, structures primarily useful in flotation, subordinately respiratory in function. Natural as may seem the assemblage included under Arthropoda, there is no group in which have introduced so much diversity of and  relations., the changes of form which changes of external conditions have promoted, are met with of very various amount. The progress of the from the first appearance of the blastoderm up to sexual maturity of the adult may be direct, without, or may be retarded by changes of form and habit, rendering the young  capable of sustaining life under very various conditions. In any one of these stages, even in the adult, multiplication may be provided for by a process of ding, the from which the new form emerges being in essence undistinguishable from the  for whose further development  is necessary. These are probably of late origin in the history of the group, their perpetuation being due to change in their surroundings. Their relations may be &ldquo;falsified by the struggle for existence,&rdquo; the details of the developmental history of the family may be crowded into a short space in the development of the individual (Ontogenesis). The description of these variations belongs to the particular treatment of the, , , and.  ARTHUR, or, a hero of the Welsh Tales, the Chronicles of Geoffrey of Monmouth, and the Romances of the Round Table. His exploits, even the most fabulous, passed with historians, before the days of historical criti cism; subsequently a reaction led to the figure of Arthur being regarded aa nothing but a Celtic myth. The truth, so far as it is possible to arrive at it, lies between these two extremes. There was a real Arthur, one of the last Celtic chiefs in Great Britain ; but there is no single trait of his real character and exploits which legends, working according to laws to be presently discussed, have not re modelled and transfigured or disfigured; while the scarcity of documents makes it impossible to reconstruct a coherent historical picture. Thus the work of comparison between the historical and the legendary personages, such as has been performed for Charlemagne by MM. Gaston Paris and Leon Gautier, is impossible in the case of Arthur. We can only study the legend and analyse its elements. There is an error, not so popular as it once was, which supposes that myths and legends arc arbitrary creations, and does not recognise them as having an origin in regular causes, and therefore a rational history, before the period when they are crystallised into their final legendary form, or are merged in the current of a literature in that later and artificial stage when it disinters and refashions old materials. Before Arthur took his final French form in the Romances of the Round Table, he was a Celtic hero in the Breton, and more specifically still in the yet earlier Welsh, legends. And behind these is the original Arthur, of whom we must 