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with specialized vitrellse and retinulse of a definite type peculiar to It is worth while bearing in mind a second possibility this grade. as to the history of the prosthomeres, viz., that the buccal =Crustacea, Chilopoda,1 Hexapod a. gnathobasic parapodia (the mandibles) were in each of the According to older views the increase of the number of three grades of prosthomerism only developed after the somites in front of the mouth would have been regarded recession of the mouth and the addition of one, of two, or as a case of intercalation by new somite-budding of new of three post-oral somites to the prse-oral region had taken prae-oral somites in the series. We are prohibited by a place. In fact, we may imagine that the characteristic general consideration of metamerism in the Arthropoda adaptation of one or more pairs of post-oral parapodia to (see a previous section of this article) from adopting the the purposes of the mouth as jaws did not occur until after hypothesis of intercalation of somites. However strange ancestral forms with one, with two, and with three prosit may seem, we have to suppose that one by one in the thomeres had come into existence. On the whole the facts course of long historical evolution somites have passed seem to be against this supposition, though we need not forwards and the mouth has passed backwards. In fact, suppose that the gnathobase was very large or the rami we have to suppose that the actual somite which in grades undeveloped in the buccal parapodia which were destined 1 and 2 bore the mandibles lost those mandibles, developed to lose their mandibular features and pass in front of the their rami as tactile organs, and came to occupy a position mouth. in front of the mouth, whilst its previous jaw-bearing References.—1. Bateson. Materials for the Study of. Variafunction was taken up by the next somite in order, into tion (Macmillan, 1894), p. 85.-2. Lankester. “ Primitive Cellwhich the oral aperture had passed. A similar history layers of the Embryo,” Annals and Mag. Nat. Hist. 1873, p. 336. must have been slowly brought about when this second —3. Korschelt and Heider. Entwickelungsgcschichte (Jena, cap. xv. p. 389.-4. Folsom. “Development of the mandibulate somite in its turn became agnathous and 1892), Mouth Parts of Anurida,” Bulletin Mus. Comp. Zool. Harvard passed in front of the mouth. The mandibular parapodia College, vol. xxxvi. No. 5, 1900, pp. 142-146.—6. Lankester. may be supposed during the successive stages of this his- “Observations and Reflections on the Appendages and Nervous tory to have had, from the first, well-developed rami (one System of Apus Cancriformis, ” Quart. Journ. Micr. Sci. vol. xxi. Hofer. “Ein Krebs mit einer extremitat statt eines or two) of a palp-like form, so that the change required 1881.—6. Stielauges,” Verhandl. d. Dcutschen Zool. Gesellsch. 1894.—7. when the mouth passed away from them would merely con- Watase. “On the Morphology of the Compound Eyes of Arthrosist in the suppression of the gnathobase. The solid palp- pods,” Studies from the Biol. Lab. of the Johns Hopkins University, less mandible such as we now see in some Arthropoda is, vol. iv. pp. 287-334.—8. Benham describes backward shifting of oral aperture in certain Chaetopods. Proc. Zoolog. Soc. London, necessarily, a late specialization. Moreover, it appears prob- the 1900, No. Ixiv. p. 976.—N.B.—References to the early literature able that the first somite never had its parapodia modified concerning the group Arthropoda will he found in Carus, Geschichte as jaws, but became a prosthomere with tactile append- der Zoologie. The more important literature up to 1892 is given in ages before parapodial jaws were developed at all, or rather the admirable treatise on Embryology by Professors Korschelt and (e. r. l.) pari passu with their development on the second somite. Heider.

Arthur, Chester Alan (1830-1886), twentyfirst president of the United States, was born in Fairfield, Vt., 5th October 1830. His father, William Arthur, when eighteen years of age, emigrated from County Antrim, Ireland, and, after teaching in various places in Vermont and Lower Canada, became a Baptist minister. William Arthur had married Malvina Stone, an American girl who lived at the time of the marriage in Canada, and the numerous changes of the family residence afforded a basis for allegations in 1880 that the son Chester was born not in Vermont, but in Canada, and was therefore ineligible for the presidency. Chester entered Union College as a sophomore, and graduated with honour in 1848. He then became a schoolmaster, at the same time studying law. In 1853 he entered a law office in Hew York City, and in the following year was admitted to the bar. In politics he was actively associated from the outset with the Republican party. When the Civil War began he held the position of engineer-in-chief on Governor Morgan’s staff, and afterwards became acting quartermaster-general of the state troops, in which capacity he showed much administrative efficiency. At the close of Governor Morgan’s term, 31st December 1862, General Arthur resumed the practice of his profession, remaining active, however, in party politics in New York City. In November 1871 he was appointed collector of customs for the port of New York. The custom-house had long been conspicuous for the most flagrant abuses of the “ spoils system”; and though General Arthur admitted that the evils existed and that they rendered efficient administration 1 The eyes of Chilopoda are not thoroughly understood, and may or may not be capable of interpretation as fitting in with those of Crustacea and Hexapoda.

impossible, he made no extensive reforms. In 1877 President Hayes began the reform of the civil service with the New York custom-house. A non-partisan commission appointed by Secretary Sherman recommended sweeping changes. The president demanded the resignations of Arthur and his two principal subordinates. General Arthur refused, on the ground that to retire “ under fire ” would be to acknowledge wrong-doing, and claimed that as the abuses were inherent in a widespread system he should not be made to bear the responsibility alone. His cause was espoused by Senator Conkling, for a time successfully; but on 11th July 1878, during a recess of the Senate, the collector was removed, and in January 1879, after another severe struggle, this action received the approval of the Senate. In 1880 General Arthur was a delegate at large from New York to the Republican National Convention. In common with the rest of the “ Stalwarts ” he worked hard for the nomination of Grant. Upon the triumph of Garfield, the necessity of conciliating the defeated faction led to the hasty acceptance of Arthur for the second place on the ticket. His nomination was coldly received by the public; and when, after his election and accession, he actively engaged on behalf of Conkling in the great conflict with Garfield over the New York patronage, the impression was widespread that he was unworthy of his position. Upon the death of President Garfield, 19th September 1881, Arthur took the oath as his successor. Contrary to the general expectation, his appointments were as a rule unexceptionable, and he earnestly promoted the Pendleton law for the reform of the civil service. His use of the veto in the cases of a Chinese Immigration Bill and a River and Harbour Bill in 1882 confirmed the favourable impression which had been made. His