STUDIES IN SPICULE FORMATION. ae 
the fusion of at-first-separate parts—such as occurs in cal- 
careous sponges, for example. 
8. With the exception of very large spicules, the nucleus 
of the distended scleroblast remains single throughout 
growth. 
9. It is a significant fact that spicule formation proceeds 
on very different lines in each of the three great groups of 
sponges—the Tetraxonida, Triaxonida, and Calcarea. 
Note.—Unless exceptional opportunities for further work 
in connection with spicule formation should present themselves 
that it is intended the present Study shall conclude the series. 
LITERATURE. 
A. PAPERS NOT CONCERNED WITH THE DrVELOPMENT OF SILICEOUS 
SPICULES. 
1. Kirxparrick, R.—‘‘ Hexactinellida: National Antarctic Hxpedition,” 
vol. ii, 1907, B.M. (N.H.). 
la. Maas, O.— Die Ausbildung des Kanalsystems und Kalkskeletts bei 
jungen Syconen,” ‘Verh. Deutsch. Zool. Ges.,’ viii Jahr., 1898. 
2. “Die Weiterentwicklung der Syconen nach der Metamorphose,” 
‘Zeitschr. f. wiss. Zool.,’ Bd. Ixvii, 1900. 
3. “Ueber die Hinwirkung Karbonatfreier und Kalkfreier Salzlés- 
ungen auf erwachsene Kalkschwimme und auf Hntwicklungsstadien 
derselben,” ‘ Archiv Entwicklung. Org.,’ Bd. xxii (4), 1906. 
4. Mincutn, lv. A.—“ Materials for a Monograph of the Ascons: I,” ‘Quart. 
Journ. Mic. Sci.,’ N.S., vol. xl, 1898. 
5. Woopianp, W.—“ Studies in Spicule Formation: I. Sycon Spicules,” 
‘Quart. Journ. Micr, Sci.,’ N.S., vol. xlix, 1905. 
B. PAPERS CONCERNED WITH THE DEVELOPMENT OF SILICEOUS SPICULES. 
6. Carter, H. J.—“ A Descriptive Account of the Fresh-water Sponges in 
the Island of Bombay, etc.,” ‘Ann. Mag. Nat. Hist.’ (2), vol. iv, 1849, 
p. $1 (the opinion is expressed that the spicules originate in the 
mesoglcea). 
“On the Ultimate Structure of Spongilla, ete.,”’ ‘Ann. Mag. Nat. 
Hist.’ (2), vol. xx, 1857, p. 21 (the spicules of Spongilla are recognised 
as arising each in one cell). 
VOL. 52, PART 1.—NEW SERIES, Ith 
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