I.' HIKOPKKMATA. 



KI'IIIXODKIIMATA. 



extremity the portion of the yolk-maw not yet metamorphosed, from 

 which the Star-Kith U afterwards to be developed; ami into the 

 cavity of this a pa*, nge U formed, through what may be termed the 

 mouth of the larva, which open* in the middle of a transverse furrow, 

 whiUt another tube paving forth from it seems to answer to an 

 intestine. On either ride of the anterior portion of the body are six 

 or more narrow fin-like appendage*, which are fringed with cilia ; and 

 the posterior part of the body is prolonged into a sort of pedicle, 

 bitobed towards its extremity, which also U covered with cilia. The 

 organination of this larva teems completed, and its movements 

 through the water are very active, before the mass at its anterior 

 extremity presents anything of the aspect of the Star-Fish; in this 

 respect corresponding with the movement* of the Pluteus of the 

 Eckiradtr. The temporary mouth of the larra does iiot remain as the 

 permanent mouth of the Star-Fish ; for it is on what is to become the 

 dorsal side of the body ; and the true mouth is subsequently formed 

 by the thinning away of the integument (which has completely 

 inclosed the yolk-maw) on the ventral surface. The young Star-Fish 

 is separated from the bipinnarian larva, by the forcible contractions 

 of the connecting pedicle, as soon as the calcareous consolidation of 

 its integument has taken place, and its true mouth has been formed, 

 but long before it has attained the adult condition ; and as its ulterior 

 development has not hitherto been observed in any instance, it is not 

 yet known what are the species in which this mode of evolution 

 prevails. The larva continues active for several days after iU detach- 

 ment ; but there is no reason to believe that its existence is prolonged 

 for any considerable time ; and as the Star-Fish is not formed by gem- 

 mation from it, but from a portion of the yolk-mass which remained 

 nnconsolidatod after it* completion, it is obvious that the larva does 

 not stand in the game relation to the Star-Fish, as the hyd reform 

 polype to its medusa-bud." ( Carpenter, ' Principles of Physiology.') 



Mullcr (' Ueber die Larven und die Metamorphose der Echiuodcr- 

 men,' 1848) has also described the process of embryonic development 

 in the Ophiurida and Eekinida. In these the embryo issues forth 

 from the ovum as soon as it has attained by the repeated segmen- 

 tation of the yolk the condition of the 'mulberry mass,' and the 

 superficial cells of this are covered with cilia, by whom agency it 

 swims freely through the water. So rapid are the processes that not 

 more than 24 hours elapse between fecundation and the exit of 

 the embryo. Shortly after its emersion tke embryo changes from 

 the spherical into a tub-pyramidal form with a flattened base ; and in 

 the centre of this bate it a depression, which gradually deepens so as 

 to form a mouth that communicates with a cavity in the inside of 

 the mass. The pyramid is at first triangular, but it afterwards 

 becomes quadrangular, and the angles are greatly prolonged round 

 the mouth (or bate), whilst the apex of the pyramid is sometimes 

 greatly prolonged in the opposite direction, but is sometimes rounded 

 off into a kind of dome. This body is strengthened by a frame-work of 

 thread-like calcareous rods. In this condition the embryo swims 

 freely through the water propelled by the cilia which clothe the 

 angles, and the projecting arms. The creature has at this stage 

 received the name of Pluteus. The Pluteus of the Ophiura and 

 ErkuHU differ but little at first in their general form and structure. 

 Each upecies however has its distinctive characters. In this stage 

 the Pluteut resembles the AcalrpAtr; its probotciform mouth 

 rmembling the Utdtutr and its cilia the BerSe, [ ACALEPIIJL] The 

 Platens gradually loses its Acalephoid characters, the jaws and teeth 

 and calcareous plates slowly developing ; and it thus pastes into its 

 true Echinodermatous form. 



t*y*rmolic Arrangement. Host systematists have given classifica- 

 tions of the f'rhimidermala. 



Link, in his volume ' Do Stellit Marinia ' (foL, Leipzig), arranges 

 and figure* a considerable number of species, in the method of which 

 the outline is here given. 



Section L Dt SUUit Fittit. 



Claw 1. Otiyaeiit (Star-Fishes with fewer than five rays). 



Genrra, Tritactit, Tetractit. 

 (.las* 2. Penladimodot (Quinquefid Star-Fishes). 



Genera, Penlayonattfr, Pentaeerot, Attroptdtn, Palmiptt, Stella 



coriacra, Sol marintu, Prntaedyloiailrr. 

 Clat* 3. PolraetiodM (Multifid SUr-Fishw). 



Genera, ffuaetu, JJeptadu, Oetaclit, Biuteaetu, Deeactu, Dode- 



Section II. Ih Hrllit Inttyrit. 

 Claa* 1. SUUanm Vermi/vrmium. 



Genera, Aelta Umbriralu, Xrlla tcolopendroidet. 

 Claw 1 SUUanm Crinilorum. 



Owen, DtctaumM, Trucaidtcamemot, Caput-Mednt-r. 

 (law 8. Atlropkyton. 



Oenera, Aracknmdet, Attnpkyton oOffOMst, Attmpbyton i-ntatum. 



Limuraa divided hit genus AHeritu into the following section* : 



1. Inttgra. Example, Aiteriat IMUO, the only species. 



J. anUaia. 'Thiswe*ic contained nit* specie*. Example, A*cri<u 



JNMMM* 



S. Mudtulm Containing six specie*. Examples, Atleriat Ophiura, 



.1 a**** KB***- 



Position of the genus between Median and Kckinut. 



Gmelin arranged the genus in three sections aho, retaining the 

 names of Lin me us for the last two ; but altering that of the first, 

 under which he includes four species, to Luna-'ir. 



Position of the genus, between Phyttopkora ami Bckintu. 



Lamarck, who, according to De Blainville, "asuivi a peu pro* 

 les erremens de Link dans la distribution systematique des Stclld- 

 rides," arranged them as the first section or family of the Echinoder- 

 matous Radiata, and separated them into the genera Comatttla, Kurt/alt, 

 Ophiura, and Aiteriat. 



Ojihiura is divided by Lamarck into two distinct sections; 1st, 

 Those species which have the rays rounded or convex on the back, 

 2nd, Those species which have the rays flattened on the back, that is, 

 above as well as below. Then comes a crowd of species under the 

 title of " E*peces que je n'ai point vues." 



Agassi z divides the Ophiura into five section* : 



1. Ophiura. Those species which have the disc very much 

 depressed, the rays simple, scaly, and furnished with very short spines, 

 and embracing or close down upon the rays. Examples, Ophiura 

 tcjlurata, 0. lacertota, Lam. 



2. Ophiocoma. Those species which differ from the preceding by 

 having very long and moveable spines upon the rays. Examples, 

 Ophiura tguamata, 0. eckinata, Lam. 



3. Ophiuretta (Fossil only). Those species whose disc is hardly 

 distinct. Examples, Ophiura carinata, Munst. ; 0. Egertoni, Brod. 



4. Acrovra (Fossil only). Differing only from Opkiura in having 

 spines on the sides of the rays instead of scales ; while the rays them- 

 selves are very slender. Examples, Ophiura pritca, Miinst. ; Acroura 

 Agouti, Miinst 



5. Atpidura (Fossil only). Having the upper surface of the disc 

 covered by a star of ten plated, whilst the rays, which are propor- 

 tionally stout, are surrounded by imbricated scales. Example, Ophiura 

 loricata, Goldf. 



Aiteriat is arranged by Lamarck under the following divisions : 



1. Those species which have the body scutellated. These are 

 numerous, and comprise the geuera Scatatlcr, Platatter, Palmatter, 

 and Matter of De Blaiuville. 



2. Those which have the body radiated, consisting of numi-mii* 

 species also, and comprising the genera SoUutrr and Pentatter ( l> 

 Blainville. 



The Stdleridoc, in Lamarck's arrangement, ore immediately followed 

 by the Echinidct. 



Cuvier makes the Echinodermcs the first class of Zoophytes, and 

 the Piklicelles the first order of that class, observing that Linn:, 'i- 

 established three genera of them (meaning apparently the three divi- 

 sions above stated), which are very natural, but numerous enough, 

 and comprise species sufficiently varied to be considered as three 

 families. 



Cuvier divides the species into : 



Let AsU5ries (Atteriat, Linn.), commonly called Sea-Stars. He 

 recognises some of the genera of Leach and Lamarck, and observe* 

 that the Encrinita (Kncrinut, Guettard) ought to be placed near the 

 Comatuhc. 



The Oursins (Echiaiu, Linn.) immediately follow the Sea-Star*. 



De Blainville divides the Stelliridians into throe families: 1. 

 Those with a stolliform body ; 2, those with a disciform Iwly ; 3, 

 those with a cupuliform body. 



I. Asteridians. 



Genus Atleriat, comprising the following divisions or sub-genera : 



A. Specie* whose body is pentagonal, and but little or not at all 

 lobated on its circumference ; the angles being fissured (Les Oreillers). 

 Example, Aiteriat Lnno. 



B. Pentagonal specie* : delicate, and, as it wore, membranous (Les 

 Palmastfries Palnipa of Link). 



C. Quinquelobated specie*, which are not articulated on the circum- 

 ference. Example, Aiteriat minuta, Linn. (Penlacerot, Link ; Atte- 

 rina, Nardo.) 



It. Pentagonal specie* more or less lobated and articulated at th> n 

 circumference (Leu Soutaitories, ou PlaUsteries). Example, At'rria* 

 Itttellata. [AsTERiAS.] 



De Blainville remarks that the species of this section, many of 

 which exist in the European seas, do not appear to him to have been 

 examined by zoologists with sufficient accuracy ; and he thinks that 

 many species have been confounded under the same name. 



f. Species deeply divided into five rays (Pentastcries). 







Triangular, depressed, and articulated on the edges (Aitropeclen., 

 Link. ; Orenattcr, Llhuyd). Example, Atteriat araitctaca, Linn. 







Triangular, rather short, and rounded above. Example, Aitcriat 

 rubent Linn. (Uraiter. Ag.) 







Rays long, strait, and often narrowed at their origin. Examples, 

 Attenat vanotata; A. granifera. Lam. 

 De Blaiaville remark* that the species which enter into tliia section 



