THE DEVELOPMENT OF ALOYONIUM DIGITATUM. 89 
18. Woodlapd, W.— “ Studies in Spicule Formation, II,” ‘Quart. Journ. 
Micr. Sci.,’ vol. 49, 1905-6. 
EXPLANATION OF PLATES 3-5, 
Illustrating Mrs. Annie Matthews’s paper on “The Develop- 
ment of Alcyoniuin cligitatum, with some notes on 
the Early Colony Formation.” 
Reference Letters of Plate Figures. 
a. Radial vertical section of very young mesentery, before it projects 
into the coelenteron. a v First developed hud of colony. A. B. Fixed 
base of polyp. An. Anterior aboral pole. b. Small blastomere. b Y . 
Radial vertical section of mesentery, rather older than stage (a.) of 
same text-fig., and stretching higher up lateral wall of polyp. b n . Second 
bud. B. Large blastomere. B. Sp. Spicules of body wall. c. Mesentery: 
somewhat older than stage (b x .) of Text-fig. 40. c v Third bud. C. Ccelen- 
teron. C. End. Columnar endoderm. C. M. Undivided central part of egg. 
C. P. Club-shaped processes of endoderm. Col. E. Columnar ectoderm. 
Col. E. C. Columnar ectoderm cell. Con. Ect. Contracted and wrinkled 
ectoderm. Ci. Cilia, d. Mesentery at a stage rather older than (c.) 
of the same figure, d. Ect. Deep columnar ectoderm in stomodseum. 
d. m. Dorsal mesenteries. D. A. Deeply staining, finely granular area 
round nucleus. D. M. Dorsal mesentery. D. M. F. Dorsal mesenteric 
filament. I). N. Delamination spindle. D. 0. Dorsal filament just 
arising as downgrowth of ectoderm of stomodseum over free edge of 
mesentery. E. Mes. Earlier secreted mesoglea. E. S. 0. Early stage 
of formation of ventral mesenteric filament, showing ectodermic band 
growing from stomodseum over edge of mesentery (Mes.). Ect. Ecto- 
derm. Ect. M. F. Ectodermic part of mesenteric filament. Ect. d. 
Deep columnar ectoderm at base of lateral wall. Ect. C. Ectoderm 
cells. End. Endoderm. End v Endoderm cells, one row deep in this 
region. End. C. Contracted endoderm. End. M. Endoderm, several 
rows deep, lining attached base of polyp. End. M. F. Endodermic part 
of mesenteric filament. End. S. Endoderm cells in region where they are 
several rows deep. /. Radial vertical section of mesentery, at time when 
stomodseal invagination is forming. F. First row of buds. G. Glass. 
G. P. Granular protoplasm. Gr. Granular, yolk free area. Gr. cell 
Group of cells becoming embedded in mesogloea. Gr. E. Granular ecto- 
derm. Gr. Gld. C. Granular gland cell. I. C. Interstitial cells. I. C. S. 
