AllTICULATA. 245 



vitality corresponds to the distribution of the members, and as therr nervous cords are sim- 

 nervous system into as many centres as there pie and not brought into communication by a 

 are corporeal segments."* With respect to the regular series of ganglions, we prefer to leave 

 agreement between the number of segments of the Rotifera and Ccelelmintha with the Entozoa 

 the body and the ganglions of the nervous sys- and Echinodermata, as a separate and higher 

 tern, it must be observed that in the higher subdivision of Cuvier's lladiata, and thus pre- 

 crustaceans, arachnidans, and insects, the gan- serve the Articulata as a distinct and well de- 

 glions, though originally as numerous as the fined subkingdom, characterized by a dispersion 

 segments, subsequently become concentrated of the nervous system in a series of ganglions, 

 by progressive development into masses which symmetrically arranged and brought into corn- 

 are fewer in number, and that also in some of the munication by a double nervous cord ; by an 

 lowest annelidans, as the leech-tribe, the ex- articulate or jointed structure of the body or its 

 ternal segments are more numerous than the appendages, by the lateral position and hori- 

 internal ganglions. zontal movements of the jaws, when these are 

 In many of the molluscous class two nervous present, and by the presence of distinct respi- 

 cords proceed backwards from the supraceso- ratory organs. The subdivisions of this sub- 

 phageal ganglion or brain, and are afterwards kingdom are not founded on the modifications 

 brought into communication by ganglionic of any single system, but principally rest on 

 masses on the ventral aspect of the body ; but the conditions of the sanguiferous and respira- 

 in the Articulata the uniting ganglions are tory organs, in connexion with exterior form, 

 always confined to the mesial line of the body, modes of locomotion and generation, 

 are perfectly symmetrical in their arrangement, I- The Cirripeds, (cirripedia, cirripeda, cir- 

 and are accompanied by a symmetrical or bila- rhopoda) ; oceanic animals called barnacles 

 teral form of the whole body. It is this homo- and acorn shells : they are characterized by 

 gangliate disposition of the nervous system their fixed condition, being either sessile, or 

 which essentially distinguishes the Articulate attached to foreign bodies by means of a 

 from the Molluscous and other divisions of the peduncle ; their generation is, consequently, 

 Animal Kingdom, and it is an infallible guide hermaphrodite, without the intercourse of se- 

 to the true affinities of the classes possessing parate individuals, but the male and female 

 it. The Cirripeda present a striking example organs are distinctly developed in each animal, 

 of this fact : these animals, on account of their The blood is colourless and is propelled by a 

 inarticulate body enveloped in a fleshy mantle dorsal vasiform heart, but the venous system is 

 and protected by a multivalve shell, were for diffused. The branchiae are internal. The cir- 

 a long time classed with the mollusca : but ripeds undergo metamorphoses, but are ulti- 

 the views of those naturalists who considered niately inclosed in an inarticulate defensive 

 that they had closer relations to the Arti- covering of shelly pieces varying in number, 

 culata, although that opinion was founded on form, and size. 



a knowledge of their nervous system only, has II. The Annelidans, (Annelida, red-blooded 



since been corroborated by every additional worms,) are always locomotive; and, conse- 



fect which has been discovered respecting quently, although hermaphrodites, they enjoy the 



them. Latreille, in his " Families Naturelles intercourse of the sexes, and reciprocally fecun- 



du Regne Animal," first placed the cirripeds in date each other. Their blood, which is gene- 



the Articulate series, but being guided by their rally red, like that of the vertebrate animals, 



adult organization, and supposing that they circulates in a closed system of arteries and 



were deficient in visual organs, and underwent veins, which sometimes has appended to it 



no metamorphosis, he joined them with the an- several well-marked propulsive cavities or 



nelidans, to form a division of Articulate ani- hearts ; they respire by means of organs some- 



mals, " Elminthoida," distinct from the " Con- times developed externally, sometimes remain- 



dylopeda," which include the insects, arach- ing on the surface of the integument, or lodged 



nidans, and crustaceans, or the Articulata with in its interior. Their body, which is of an 



jointed feet. The later researches of Mr. I. V. elongated form, and covered with a soft skin, 



Thompson and Dr. Burmeisterf have proved is always divided into numerous transverse 



that in the immature state the Cirripeds un- segments, of which the first, called the head, 



dergo repeated metamorphoses or moults ; that scarcely differs from the others, except by 



they move freely in the water by means of the presence of the mouth and of the principal 



setiferous articulated members, and during this organs of the senses. Many possess branchiae, 



period guide their wanderings by the aid of arranged the whole length of the body, or situ- 



distinctiy developed, though simple eyes. ated at the middle ; others, which for the most 



Besides the cirripeds the higher organized part inhabit tubes, have the branchiae collected 



infusoria and intestinal worms have been at the anterior part of the body; in others, 



proposed by some naturalists to be added to again, the respiratory organs are in the form of 



the articulate division of Animals : but as they internal air sacs. The annelidans never possess 



are neither articulated nor possess articulate articulated limbs, but many have, instead thereof, 



stiff bristles, or hooks, frequently inclosed in 



See his celebrated memoir, " Sur un nouveau tubular prolongations of the integument, 



rapprochement a etablir entre les classes qni com- The other articulate ciouet. viz invert* 



posent le regne animal." " Annales du Mwt&um. \ -, Articulate Classes, viz., insei ts, 



d'Histoire Naturelle, 4to, torn. xix. p. 73. arachnidans, and crustaceans, differ from the 



t Beitrage zur Naturgeschichtc der llankeufuesscr, preceding classes in the possession of arti- 



4to. Berlin, 1834. culated limbs, terminated by claws ; and in 



