392 MR PATRICK GEDDES AND MR FRANK E. BEDDARD 
same pedicellariz in two other species of sea urchin (Spherechinus granularis 
and Echinus melo). He considers that their function may be to secrete mucus. 
Our account of the structure of these pedicellariz substantially bears out what 
has been said by him. There is, however, some difference of detail, owing, no 
doubt, to the different species that have formed the subject of Mr SiapeEn’s 
investigation and our own, and we do not in all cases completely understand 
his figures. For example, on Plate XIII. fig. 10, of his paper, a transverse 
section of one of these pedicellariz is given, in which there is no trace of the 
calcareous valves, nor is their position indicated. 
We have been unable to make out in our own preparations the complex 
nervous arrangement described and figured by Mr SiapEn, although his results 
seem to be corroborated by those of Messrs RomAnes and Ewart,* who de- 
scribe a complete nervous system of fibres and cells in the pedicellarie, as well 
as in the spines. These structures may perhaps correspond to what we have 
figured at Plate X XI. fig. 10. 
The fourth and last variety of pedicellariz which are found in this urchin are 
the trifoliate. These are exceedingly small, but their structure can be tolerably 
well made out without the aid of sections. They resemble very closely the ophio- 
cephalous and tridactyle pedicellariz, but do not possess coiled plates or loops. 
The whole pedicellaria is shown on Plate XIX., and Plate XXI. fig. 18, 
shows the head and part of the stalk more highly magnified. 
Observations made upon the structure of muscular fibres in the Echinoderms 
have been up to the present time entirely contradictory. Wagner, t Von 
SIEBOLD, { and JoHANNES MUuueER§ have asserted that there is no appearance 
of transverse striation. VALENTIN, on the contrary, in his monograph on the 
sea urchin, || maintains that the muscles of the spines and of the lantern are 
really striated, and De QuATREFAGES‘ has seen a transverse striation on the 
longitudinal muscles of Synapta. On the other hand, BavEr** has contradicted 
these observations, while Lrypictt has described a longitudinal and transverse 
striation in Echinus and Holcthuria. 
Finally, in the latest work on the subject—that of M. Freprr1cQg—the 
striation of the muscles of the lantern of Echinus sphera is denied.{t How are 
all these contradictory statements to be reconciled ? 
* Romangs and Ewart, loc. cit. 
+ “ Ueber die Anwendung histologischer Charactere auf die Zoologische Systematik,” Arch, Anat. 
iind Phys., 1835, p. 319. 
}{ Anat. Comp. p. 81. 
§ “Ueber den Bau der Echinodermen,” Arch, Anat, iind Phys., 1853, p. 319, 
|| Op. cit. p. 101, 102. 
{ Sur le Synapta, “ Annales d. Se. Nat.” 1842, vol. xvii. p. 43, 
** “ Beitriige zur Naturgeschichte der Synapta digitata,” Nova Acta Acad, Cs, Leop, 1864, vol. 
Xxxl p. 25. 
++ “Kleinere Mittheilungen zur thierischen Gewebelehre,” Arch, Anat. und Phys. 1854, p. 305. 
tt “ Contributions a l’étude des Echinides,” Arch, de Zool. Expérim., vol. v, 1876, p. 439. 
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