KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 19. N:0 7. 47 



It follows from what has been cletailed here, tliat the phyllodean pedicels of the 

 great majority of the Spatangidte, when forming, begin with a circulai' top, sti^engthened 

 by a central calcareous network, that is, by a contrivance like that wliich is permanent 

 in the Archteonomous Echinoidea, and chiefly subserves locomotion, but that they soon 

 pass through this stage, as transitory, and develop into organs of a higher function, 

 that of touch. 



The distribution of the phyllodean pedicels among the iive ambulacra, and the 

 form of the phyllodes, are different in the different genera. The two bivious ambu- 

 lacra I and V always symmetrise with one another in this, as do also the two paired 

 ones, II and IV, while the front ambulacrum III, the odd one, stånds alone. Whenever 

 the tAvo series a and b differ in the number of their phyllodean pores, it is the uni- 

 porous series, I h, II h, III a, IV 6, V a, that presents the additional pore, all in 

 accordance with the universal rule. The two paired ambulacra of the trivium, II and 

 IV, present the most highly developed phyllodes, and the greatest number of phyllo- 

 dean pedicels. In Maretia planulata these are seen to number eleven in each series, 

 in Meoma ventricosa ten, in Brissus Scilla3 nine, in Desoria australis eight, in x\gassizia 

 scrobiculata seven, in Spatangus purpureus six, in Breynia australasiffi, Plagionotus 

 pectoralis, Faorina chinensis and Schizaster fragilis, five. On the other hand there 

 are only four in Brissopsis lyrifera, Moira atropos and Abatus Philippii, three in Mi- 

 craster cor anguinum, Kleinia luzonica, Echinocardium cordatum and Lovenia elongata. 

 But still the number always equals, often exceeds that of the corresponding pores in 

 the bivium. In the frontal ambulacrum the number of phyllodean pores is often less 

 than in the bivium, in a few cases it equals them, and in still fewer exceeds them 

 slightly, as in Brissus Scillfe, Plagionotus, Brissopsis, Maretia planulata. It follows 

 from this that the floscelle has its greatest extension in the transverse direction. 



In each phyllode the pedicels are largest in the proximity of the peristome, the 

 more remote gradually becoming smaller, and less rich in filaments. They are, however 

 rather suddenly replaced by simple pedicels, small and slender, terminating in a conical 

 or truncated top, which, in most cases, is surrounded by a waved margin, as in Bris- 

 sopsis Ija-ifera, Pl. IX, fig. 83, 84^ Moira atropos, Pl. X, fig. 110, Lovenia elongata 

 Gray, fig. 107, 108, Schizaster japonicus Al. Ag., fi.g. 111, and thus somewhat like the 

 pedicels in Rhynchopygus pacificus Al. Ag., Pl. XI, fig. 118, 119. These simple ventral 

 and lateral pedicels become very slender and minute, more particularly in the bivium 

 and the paired trivious ambulacra, and their pores are very small, all up to the petal. 

 In the bivium, however, this holds good only with regard to the exteriör rows of plates, 

 the I b and V a. The two interiör rows, I a and V b, very generally have their series 

 of simple pedicels interrupted by the sudden appearance of the stout, peculiar, subanal 

 pedicels discovered by Johannes Muller. Introduced in the earlier Spatangidaa, the 

 Prymnadetes, in an uncertain and, as it were, a hesitating manner, these pedicels be- 

 come in the Prymnodesmians a constant and striking feature. The subanal fasciola, 

 in traversing the bivious ambulacra, ^) marks off their five foremost plates, 1 — 5, and 

 ') Études, p. 15, 59; pl. XXXIT, fig. 200, — XLIII, fig. 232. 



