STUDIES IN SPICULE FORMATION. 303 
List oF THE WORKS REFERRED TO IN THE TEXT. 
1. A. von Kottrker.—‘ Icones Histologice,’ Leipsig, 1864. 
2. G. von Kocu.—‘“ Anatomie der Clavularia prolifera,” ‘Morph. Jahrb.,’ 
Band vii, 1881. (There are other papers by von Koch on Aleyonaria 
in the same journal from 1878 to 1881.) 
3. A. Kowatevsky and Marton. —“ Documents pour l’histoire embryogénique 
des Alcyonaires,” in ‘Ann. du Musée d’Hist. Nat. de Marseille,’ i, 
1883. 
4, K.C. M. Scunerper.— Hinige histologische Befunde an Ccelenteraten,” 
in ‘Jena. Zeitschr.,’ xxvii, 1892. 
5. S.J. Hicxson.—“ The Anatomy of Aleyonium digitatum,” in ‘ Quart. 
Jour. Micr. Sci.,’ vol. 37, 1895. 
6. G. C. BournE.—“ Studies on the Structure and Formation of the Calea- 
reous Skeleton of the Anthozoa,” in ‘ Quart. Jour. Mier. Sci.,’ vol. 41, 
1899. 
EXPLANATION OF PLATES 16 & 17, 
Illustrating Mr. Woodland’s paper, “Studies in Spicule 
Formation.” II. 
Figs. 1—7 and 18—22 magnified about 950 diameters. 
Figs. S—15 magnified about 475 diameters. 
Figs. 16 and 17 magnified about 450 diameters. 
PLATE 16. 
Fic. 1 shows scleroblasts containing spicules at their first appearance. 
Fic. 2 shows young spicules, in which the pink-staining central organic 
core has become distinguishable from the peripheral layer. 
Fie. 3.—The scleroblast nucleus has here divided, and the young spicule 
has in consequence assumed an elongated form. The nuclei, it will be 
noticed, tend to be situated at the opposite extremities of the sclerite. 
Fic. 4.—The extremities of the spicule are becoming divided up into 
processes. 
Fie. 5 shows the typical ‘‘ caudal vertebra” form of spicule, 
