KONGL. SV. VET. AKADEMIENS HANDL. BAND 19. N:0 7. 43 



as good as an)^ given since. ^) He was also acquainted with another sort of pedicels, narnely 

 those belonging to the frontal ambulacrum of Echinocardium flavoscens, and possessed 

 figures of these, made by his brother and draughtsman C. F. Muller. These figures, 

 however, were not published till long afterwards, in 1789, by Abildgaard ") Avho was 

 well aware of the distinctness of the frontal pedicels from those surrounding the mouth. 

 It will seem that O. F. Muller had regarded both as being of one and the same sort, 

 when he made use of their structure, very happilj^ after all though, as an essential 

 character distinguishing his genus Spatangus: ^)tentaculis ijenicillatisi>, from the genus 

 Echinus: Hentaculis shnplicibus^u ^) This is indeed the first important step towards a 

 rational dismemberment of the great Linna-an genus Echinus, and O. F. Muller is to 

 be considered as the real author of the natural genus Spatangus since adopted by 

 Lamarck. The name, borrowed from Aristoteles, had been in use with the Museo- 

 graphers of the pre-Linnsean era for certain artificial divisions. 



It is, however, mainly to the account given by Johannes Muller"') of the various 

 kinds of pedicels occurring in the Echinoidea, that Ave have to turn for the principal 

 source of information respecting these important organs. After having remarked that 

 not all the regular Echinoidea are homoiopodous, that is, have the whole of their pedicels 

 terminating in a sucking-disk, as Duvernoy had presuined, but that certain genera, as 

 Echinocidaris, Astropyga, Diadema, and Colobocentrus, have the dorsal pedicels simply 

 pointed and flattened, and, the last named genus excepted, plaited on the sides, thus 

 suggesting a respiratory function, he proceeds to give the folloAving general description 

 of these organs, as they occur in the Spatangidaä. In this group four different kinds 

 of pedicels may be distinguished: 1) simple locomotive pedicels with truncated or 

 rounded tops, destitute of sucking-disks; 2) locomotive pedicels provided Avith a terminal 

 circular sucking-disk, either crenulated at the margin and strengthened inAvardly Avith 

 radiating calcified laminse, or divided into radiating processes containing calcareous 

 rods or lamels; 3) tactual, penicillate pedicels, ending in expanded brushes of club- 

 shaped filaments, inwardly sustained by calcareous rods; 4) branchial pedicels, ambulacral 

 gills, having the shape of triangulär leaflets Avith plaited sides. In one and the same 

 ambulacrum there may be found tAvo or eA^en three of these kinds succeeding one 

 another, between the peristorae and the dorsal pole. Wherever a fasciole is present, one 

 kind of pedicels is peculiar to the area it circumscribes. In the genus Spatangus Joh. 

 Muller recognises three kinds: tactual, locomotive and bi"anchial. The circum-oral 

 pedicels of all the five ambulacra are tactual and penicillate, the rest of the ventral ones 

 simple and locomotive. Within the sub-anal fasciole there stånd on either side three 



') Zoologise Danicfe Prodromus, 1776, p. XXIX. — Zoologia Dauica, I, t. VI, fig. 5, 1777; latin letter- 

 press, in 8:0, 1779, I, p. 11; in fol., 1788, p. 5; danisli letterpress, in fol., 1781, p. 19. The 

 erratum, Zool. Dan. Prodr. p. XXIX: «ano infero», is liere corrected to »ano laterali». 



^) Zool. Dan. Ill, p. 17, t. XCI, fig. 4. »Terminantur disco radiato, radiis clavatis, alternis longioribus. 

 Tentacula vero, qute porös ad circnmfereutiam oris transeunt fascioulo penicillato filamentis oapitatis 

 composito terminantur», Abildg. 



3) Zool. Dan. Prodr., p. XXIX. 



*) Ueber den Bau der Echinodermen. Abbaudl. d. K. Akademis d. Wissenscb. in Berlin, 18,54, sep. p. 26, 

 pl. III. 



